Hits:  since 20050614

HF-, VHF-low, UHF- and SHF- band Beacons

Most recent measured  "mark" QRGs underlined:

Tout door/kHz 10 m GPSDO-BCN  10 m BCN 6 m BCN 4 m BCN 70 cm BCN 23 cm BCN  13 cm BCN  3 cm BCN
+20 °C
T-amb +24 C
28 800.00000 28 228.58 50 033.138 70 032.87 432 434.58 1296.934.36 2320 932.87 10368 939.72
T-Lo +45 C
+15 °C
28 800.00000 28 228.43 70 032.97 1296.935.4 T-Lo +37 C
+10 °C
T-amb +17 C
28 800.00000 28 228.41 70 033.04 432 434.90 1296 935.34 T-Lo +36 C
+5 °C
28 800.00000 28 228.42 70 033.04 432 434.94 1296 935.37 T-Lo +35 C
0 °C
T-amb +15 C
28 800.00000 28 228.42 70 033.03 432 434.96 1296 935.34 2320 934.52 T-Lo +35 C
-5 °C
28 800.00000 28 228.38 50 033.058 70 033.05 432 434.91 1296 935.35 T-Lo +34 C
-20 °C
28 800.00000 T-Lo +34 C

Measured frequencies were referenced to GPSDO frequency standard.
Equipment used: MT8802A locked to GPSDO reference.

Ambient temperature of beacons on 28, 50 and oscillators of  2320 and 10368 MHz bacons varies seasonally between +14 °C and +24 °C. 432 and 1296 MHz beacons are more affected as ambient temperature varies between +5 °C to +20 °C.  28.8 MHz GPSDO beacon is immune to temperature variations.

Try your DSP FFT display on these at great ranges!

OH5SHF Beacons' ODXes

70 cm:  OK2BFH  1340 km
(BCN spotted 7 x)
10 m:
KE4WBO   8273 km 
(BCN spotted 166 times in 2010)

OH5TEN bcn:  SV1ATJ  2559 km
(BCN spotted 4 x)

23 cm:  OK2BFH   1340 km
(BCN spotted 6 x)
6 m:  CN8LI   3828 km
(BCN spotted 292 x)
13 cm: SP4MBP  866 km
(BCN spotted 1 x)
4 m:   CT1HZE  3606 km
(BCN spotted 94 x)
  3 cm: SM0DFP 437 km
(BCN spotted 2 x)

Passive inter-modulation (PIM) forced 28 MHz beacon to move down in QRG in 2008

Since the grouping of 28, 50, 432, 1296 MHz beacons with the 145 MHz repeater to the same site and mast was done, during the cold months a sporadically appearing, sometimes strong PIM (passive intermodulation) signal, was generated on the 2 m FM repeater's input once the repeater was keyed on, keeping the repeater from going QRT. The interference on the repeater's receiver was a complex sum of harmonics of 28 and 50 MHz beacon's FSK keying, cut off by 432 MHz CW keying. The mixing product was not generated in any of the transmitters, but by some metal junction in the mast structure of the closely spaced antennas on a spot that I was unable to pinpoint. The PIM disappeared once the 2 m repeater's TX was off, but the 145 MHz repeater TX's QRG had no effect on the PIM QRG, which occurred in the 2 m repeater's RX input some 5 kHz below the input Fc of 145.100 MHz.

The 145 MHz repeater's antenna was radiating enough energy to make the PIM-causing metallic junction to go unlinear in the mast structure, probably located in one of the antenna mounting clamps (Aluminium tubing and S.S. or galv. steel clamps and always on mid winter cold days). The PIM QRG moved with QRGs of 28, 50 and 432 MHz beacons, but of those, the 28 MHz beacon's harmonic, which was one of the factors in the formula of the PIM QRG, was the second highest harmonic (4th) and thus, a smaller QRG change was required to move the PIM QRG down and outside 145 MHz repeater FM RX IF filter's bandpass by about 10 kHz, not to mention 28 MHz beacon band was the easiest to re-allocate a new QRG compared to 6 m.  Fpim[MHz] = (4*28.2315 MHz) - (8*50 MHz) + 432.435 MHz.. When the new 28 MHz beacon QRG was implemented, the PIM resides now outside repeater's input bandwidth, on 145.086 MHz  +- 1 kHz (wobbled by beacons' QRG's annual frequency drift).

To cure the problem without creating new problems by too radical changes, the Radio Club of Kouvola, OH5AG kindly bought a new crystal for the 28 MHz beacon's TX for 28.2285 MHz. The PIM  has not been heard since on the repeater's input, after the QRG change to 28.2285 MHz was implemented in Aug. 2008. The antennas of six beacon's and 145 MHz FM repeater are all stacked on the same 6 m  mast.

Ham , BC & air frequencies in KP30: Link to: Six and Ten Reporting Club
114.599 MHz 200 W  ERP UTTI VOR, AM CW ID: "UTT"+voice
105.700 MHz  30 kW ERP Radio Nova RDS: 6209 __NOVA__
102.700 MHz  30 kW ERP The Voice RDS: 62AB _VOICE__
 99.500 MHz  30 kW ERP FSR Mix RDS: YLE_X3M_ YLE_VEGA
 96.900 MHz  30 kW ERP YLE Radio Suomi 6203 YLESUOMI
 92.800 MHz  30 kW ERP YLE X RDS: 6202 __YLEX__
 88.500 MHz  30 kW ERP YLE Radio 1 RDS: 6201 YLE_YKSI
 70.033 MHz  15 W  ERP
 50.033 MHz 100 W  ERP
 28.800 MHz   2 W  ERP
 28.2285MHz  50 W  ERP

Send reception reports to DX-Summit

            We also QSL (OH5SHF OH5TEN OH5RBG    via OH5IY )

Beaming SW towards Central Europe from 65 mAAT

OH5SHF's 28 MHz  beacon's ground wave coverage. Computed signal strengths (S-units) with 6 dBd RX antenna at 25 m AGL, S 1 = 0.2 uV (-121 dBm). Note:  the noise level is higher on 28 MHz and HF receivers are not  typically built to be as sensitive as 50 MHz radios, and unfortunately are most insensitive in particular on 10-meter's band.; expect signal/noise ratios much lower on 28 MHz than on 50 MHz

OH5SHF's 50 MHz  beacon's ground wave coverage. Computed signal strengths (S-units) with 8 dBd RX antenna at 25 m AGL, S 1 = 0.2 uV (-121 dBm)

"Corrected" Tropospheric Path Loss = TX ERP [in dBm] + RX Ant. Gain [dB]  -  RX feed line loss [in dB, often negligible] - antenna height loss  [in dB, see graph below] -  -145 dBm [CW RX sensitivity level] - band noise above 290 K [in dB, from upper graph per  your location's man-made noise level]

It is expected your RX system Noise Figure is substantially below 3 dB! (RX k curve)

Using the calculated Corrected Tropospheric Path Loss value, you are able to determine the approximate maximum range (CW mode) from upper graph (signal received 50% of time).

Note: the "Corrected" Path loss here is used include effects that reduce RX S/N ratio specially on 50 and 28 MHz due to higher noise levels on those bands to get the true range and not just pure path loss. If you need only the path loss for shorter range to estimate signal level when S/N is not an issue, do not correct for band noise!

Note: Range can be reduced by lower TX and/or RX antenna's height,  terrain and other obstructions and by factors such as poor RX system Noise Figure, higher local noise level which to some degree can be corrected using the graphs.

ICEPAC - Predicted F2 prop. 23 Dec. 04 UTC, solar cycle maximaICEPAC - Predicted F2 prop. 23 Dec. 10 UTC, solar cycle maxima
ICEPAC - Predicted F2 prop. 23 Dec. 16 UTC, solar cycle maximaICEPAC - Predicted F2 prop. 23 Dec. 22 UTC, solar cycle maxima

F2-layer propagation coverage for the 28.2285 MHz beacon.

ICEPAC - Predicted Es prop. 23. June morning

Es layer propagation coverage for the 28.2285 MHz beacon (contours: dBm at RX input, all plots calculated for 6 W TX output).

28 & 50 MHz dual-band dipole antenna

This low-gain, almost omnidirectional antenna works both on 28- and 50-MHz bands. The 28 & 50 MHz beacons were to be fed via diplexer through just single common 50-ohm coaxial feed line, which called for a dual-band antenna. The CAD parameters I used to design the antenna, concentrated on optimizing to low VSWR only at band ends but ignoring radiation pattern, since directional gain was not desired. It is basically a "poorly" designed LPDA" (log periodic dipole array) with very low tau-parameter (short boom and few elements) and no feed-line terminating stub. Contradictory to proper LPDA designs, it has a big un-orthodox frequency-gap where it performs bad - between the lowest and highest operating frequencies, but that is just the idea. Why add weight and wind load to cover the 30...48-MHz range, when it is not needed for this ham radio beacon?

The CAD model used 1.4 mm enameled wire as elements and 4 mm brass welding rods as phasing line. Prototype antenna's element wires were stuffed inside four pcs of 3 m long telescopic fiber-glass fishing poles (2.50 € a piece), but in spite of being a prototype, it has survived the elements since September 2003 at the beacon site.

Dual-band beacon antenna's construction details

Computed 50 MHz gain was 1.5 dBd and F/B ratio 2.5 dB and on 28 MHz, the gain was 0.1 dBd and F/B- ratio 0.4 dB in free space, however antenna is mounted just 6 m above the roof.

Mechanical construction for such antenna includes insulator-supports for the 200-ohm open-wire phasing line, long aluminum element brackets to alleviate torque of fragile (center reinforced with short fit-inside PVC tube sections) fishing poles and finally, shielding the feed-connections from moisture and making sure the poles can not get filled with water - open ends - waterhole at center. The feed uses a ferite sleeve balun, many small toroids over RG-58 inside a heat shrinking tube installed inside the boom. This would call for a DC-shorting arrangement (perhaps a shorted "quarter-wave" stub after the ferrite sleeve, 1.24 m of RG-58 - but I have not verified how it affects SWR) so I recommed using a proper balun-transformer that works for 28 and 50 MHz both, instead. Don't forget to connect the feed line's shield to the boom, or mast for grounding.

The excess voids on fiber-glass poles' tips were cut off to reduce overall antenna size, wind and snow loads. The elements could also be made of aluminum tubing - then the element lengths should be shortened a little. Making it even more light and small it could also be mounted pointing upwards (at 90 degree tilt angle) by bolting the element brackets directly to the side of a mast (with no boom) - price: about 2 dB of ERP lost towards horizon on 50 MHz and 95 cm reduced height for either of  the elements.

Unless traps and loading coils are use, this may be the smallest "full-size" antenna that works both on 28 and 50 MHz since only 8.6 m (incl. boom) of tubing material is used. In comparison, a GP with trap and proper (3) radials for both bands needs some 14...15 m of element material and a GP can only deliver vertical polarization. This dual-band antenna can be used as vertically, or horizontally polarized. If set for vertical polarization, it is practically omnidirectional. Two such crossed antennas could be phased for circular polarisation. The same basic LPDA-style idea could be adopted for a set of any multiband HF, VHF or even UHF ham beacons fed with just single coaxial.

OH5SHF's 10 & 6 m antenna

28 & 50 MHz SWR

OH5SHF beacon's rack:
top: 28 V 10 A SMPSU, 6*IRF510 FET 28 MHZ PA
10 GHz LO and 2.3 GHz LO ovened synthesizers w. int. G4JNT keyers
12 V 5 A SMPSU, 50 MHz: home brew TX w. Misubishi RF-hybrid, 28 & 50 MHz G4JNT keyer, 12 V 3 A SMPSU, Multitone TA8 28 MHz TX
100 W  8*IRF510 FET amplifier for 50 MHz with 28 V 20 A SMPSU
bottom: 100 W  8*IRF510 FET spare amplifier common for 28 & 50 MHz bands with 28 V 20 A SMPSU

68 W (@ 7.2 W drive 07-2014) of 28 MHz  and 100 W of 50 MHz  are connected via coaxial coupler to RG-8 antenna cable.

145 MHz FM repeater since 1992: modified Televa 700 repeater base-station, w. home made PSU&duplexers, RyydLab controller w. OH3NYB SW.
The discarded original repeater from 1978 consisted of valve TX from Motorola Consolette base station, OH3WZ TTL controller and Motorola Dispatcher (Motorola CD-100 from 1987-1991) RX
integrated by OH5QA(s.k.)'s team: OH5QO (s.k.), OH5FP and others and the duplexer milled by Antero Toivonen (dec'd.).

Pre-  Nov. 2013   28 & 50 MHz TX combiner filter (good for up to 20 W max)

28 & 50 MHz TX spectrum at diplexer output via 50 dB coupler, 10 dB/div, span 2...100 MHz

10 m and  6 m TX antenna stub coupler
Another way to feed 28 and 50 MHz transmitters to same antenna cable with less losses.
Currently in use at OH5SHF, good for 100 W.

Few things to pay attention to: the stub on 28 MHz TX branch is mostly to keep 50 MHz matching good, 28 MHz TX has always LPF, which attenuates maybe 20 dB the 50 MHz signal, thus reducing transmitter created IMD products - one stub should be enough. However, typical  50 MHz  TX's LPF does not attenuate 28 MHz TX power and broad band power amplifier output transformers pass 28 MHz all the way in to the semiconductors and the 50-28=22 MHz transmitter created IMD product gets also passed out un-attenuated. The sum product at 78 MHz is not attenuated by the 50 MHz LPF very much either. The coupler has two stubs to attenuate 28 MHz signal by 66 dB from entering the 50 MHz TX. Quarter wavelength jumpers and stubs could be added on branches, if seen necessary to further increase attenuation, but even one stub / branch could be enough.

The construction can be made with T- connectors of preference (N, Amphenol, TNC, BNC....) or from  plumbing parts, but they may be as expensive as coaxial adapters and need a lot of soldering work.
Neither can any coaxial sections be changed with ease.

It is worth while to note that higher impedance cable has less capacitance and should be used in the stubs, even 150 ohm cable, if available.
The coupler I built, uses RG-62 in the stubs and RG-213 on 1/4 wave length jumpers, RG-58 (note the cable power limits) could be used as 28 MHz jumper, but not preferred on 50 MHz branch due to higher losses.
It you have T&M gear, or antenna analyzer, use it in cutting the stubs and jumpers, though for known cable types, simple math (((300 / MHz) / 4) * Vf) and metric tape scale works too.
It would have been too easy, if no extra trick would not be required: the 28 MHz port impedance is too low (because of the adjacent 1/4 wave length stub for 50 MHz), so the 28 MHz port needs LC- match to make SWR and losses good, 50 MHz port is fair with out any additional match network.

The values given are with 50 ohm dummy load as antenna. If the antenna has mismatch, it will reflect on TX port(s) SWR and a little bit on losses. The 28 MHz port LC- match gives some possibilities to compensate for antenna SWR by compressing - stretching the coil. Another form of match could be used if one likes to use variable capacitor there, from 28 MHz TX side: nominally 87 pF to ground and 7 turn coil in series (untested).

 The same scheme works scaled to other frequency pairs, if they are separated proportionally by the same amount. Quarter wave open-end stubs behave as "shorts" also on uneven harmonic frequencies, so it may not always be possible to use the stub coupler and if the difference in frequency is big enough, T- structure LC high pass - low pass filter is a working method. Too closely spaced frequencies call for cavities and anti resonance reactive components, as used in repeater duplexers. There are also compact commercial TX couplers manufactured for VHF and up.

Initial data from 1st summer Es season wth FET PAs comparing to 2013:
- 28 MHz: 6 dB power increase changed the number of DX spots by -50%
- 50 MHz:  6 dB power increase changed the number of DX spots by +18%

OH5RBG's 70 MHz  beacon's ground wave coverage. Computed signal strengths (S-units) with 8.5 dBd RX antenna at 25 m above average ground level with unobstructed take-off, S 1 = 0.2 uV (-121 dBm) @ RX input.

The 70 MHz beacon was built during fall of 2009 with latest technology: USB-controlled synthesizer, PIC-based PC-configurable keyer and MMIC driving the FET PA. The basic scheme works for all bands from 28 to 70 MHz with just modifications to driver LPF and PA stage coils and capacitors - the single-ended FET PA is narrow-band type. Using the 175 MHz application sheet for RD06HVF1 FET, the beacon can be built for 144 MHz operation also. 432 MHz model would need different version for the synthesizer chip - the faster LVDS reaching up to 910 MHz.

The first built beacon module was for 40 MHz, but uncertain and troublesome licencing caused a rebuild to 70 MHz (took some 2 h) which has been a ham band in Finland since 4th Nov. 2009. The enclosure holds the 70 MHz beacon TX module with G4JNT keyer and a 4.5 A SMPSU. FET PA feeds some 5 W to a horizontally polarized low-gain (7 dBi) antenna (Aerial AV1462-70) beaming Az. 232° (SW for sporadic-E propagation) mounted on a cellular tower on a hilltop 131 m + 8 m ASL and delivering 15 W of ERP.


In detail, the synthesizer, which is configurable for any QRG from 3.5 to 260 MHz in 1 Hz steps (and for exact FSK shift) via the USB connection, delivers a 0 dBm (square wave) fed via 2- section LPF to ERA-5SM MMIC amplifier. G4JNT RS-232-configurable PIC-keyer keys the SDR-Kits USB-synthesizer. The +16 dBm drive feeds a low-cost SWR tolerant Mitsubishi PA FET delivering 5 W RF-output. The output is filtered with several LPF stages, one for UHF for added attenuation on cellular frequencies (harmonics are attenuated by 119 dBc on 900 MHz UMTS band). Total currrent is monitored with a 2 A analog panel meter. The antenna output circuit has a 230 V gas-disharge tube, 2 kV series capacitor and antenna connector & case bonded to site ground bar.

OH5SHF's 432 MHz  beacon's ground wave coverage. Computed signal strengths (S-units) with 18 dBd RX antenna at 25 m above average ground level and take-off clear of trees, S 1 = 0.2 uV (-121 dBm) @ RX input (needs a pre-amp.).

OH5SHF 1296 MHz  beacon's ground-wave coverage. Computed signal strengths (S-units) with 21 dBd RX antenna at 25 m above average ground level and take-off clear of trees, S 1 = 0.2 uV (-121 dBm) @ RX input (needs a pre-amp.).

OH5SHF 2320 MHz  beacon's ground-wave coverage. Computed signal strengths (S-units) with 24 dBd RX antenna at 25 m above average ground level and take-off clear of trees, S 1 = 0.2 uV (-121 dBm) @ RX input (needs a pre-amp.).

OH5SHF 10 GHz  beacon's ground-wave coverage. Computed signal strengths (S-units) with 30 dBd RX antenna (0.8 m dish) at 23 m above average ground level and take-off clear of trees, S 1 = 0.2 uV (-121 dBm) @ RX input.

OH5SHF's UHF and SHF antennas, the 432 MHz 2-by-2 dipole stack: Aerial AV1525 array without the reflector grid, 1296 MHz two-wavelength "Alford Slot" (slotted cavity antenna) , 2320 MHz 15.5 dBd gain 8-Quad loop reflector panel sector antenna inside a 110 mm Polypropylene pipe radome and 10 GHz UKW-Berichte omni WG-slot antenna also inside a 50 mm Polypropylene pipe radome.

10-2010->4-2014 28 MHz 28.8 MHz 50 MHz 70 MHz 432 MHz 1296 MHz 2320 MHz 5760 MHz (U.C.) 10368 MHz
TX Pout +48 dBm,
62 W
+33 dBm,
2 W
+49 dBm,
75 W
+37 dBm,
5 W
+40 dBm,
10 W
+40 dBm,
10 W
+29.3 dBm,
0.83 W
+31.2 dBm
1.3 W
+27.4 dBm,
0.55 W
Refl. coeff, VSWR -14 dB,
pi-match -26.5 dB,
-14.6 dB,
-18.4 dB,
-15.6 dB,
<-16 dB,
1/1.37 or better
tuned for best ERP
Pant, ERP 45 W,
2 W,
1.5 WERP
46 W,
4 W,
8.4 W, 
26.5 WERP
8.3 W,
0.68 W, 
30.4 WERP
1.3 W,
0.5 W,


Aerial's AV1525, two of such are used in OH2UHF, is basically a directional antennal with gain of 7.3 dBd and high F/B-ratio. We wanted to get more omnidirectional-style coverage but little ERP towards 130..180 degree zone. The solution was to abandon the two-wavelength ominidirectional cavity slot aerial and use a rugged commercially made second-hand (abt. 35 years in-use, but in pristine condition) dipole array and point the main lobe with most ERP towards WSW (SM7-/SM1-/SM0-/SM5- area), where most of the long-haul cluster spots come from and which iluminates the path of Baltic Sea tropo openings to DL and OZ etc. The illumination of southern OH5 and UA1-/ES border is reduced and St. Petersburg is just on the edge of the lobe as are OH6- and SM2-, but that is unavoidable without using more hardware in the form of extra gap-filler aerial.

The omission of the hefty bolt-on refector-grid reduced antenna's wind area (0.45 to 0.2 m2) and decreased the F/B from 20 dB down to 5 dB which gives enough ERP (about 5 W) towards NE sector for adequate illumination of OH7-/OH4- and eastern OH5-. The AV1525 horizontal support boom acts as a long reflector element and produces the 5 dB F/B and gives about 2 dB of more gain than the closely spaced dipoles alone. There are no stations beyond 200 km towards NE, so we do not spend more of the limited ERP for that area. The SWR of AV1525 ("P") is better than 1:1.5 on 432 MHz without the reflector and this antenna is insensitive to sleet & snow. The AV1525 is fed with 12 m of Ecoflex 15 cable.

1296 MHz beacon radiates from the controversial Alford Slot antenna, which delivers horizontal polarization and is practically omnidirectional (F/B: <3 dB), with slot facing towards azimuth 240°. If there is something good in it, this antenna fits to a 50 mm diameter radome where no quad loops or ordinary dipoles fit inside. The cavity slot's radome is now a black PVC tele cable protection pipe with 2.5 mm wall thickness. The antenna is fed with 7 m of Heliax LDF-4-50A through a 1/4-wavelength inside-the-cavity UT141 spliced balun. The SWR was improved during a service break in fall of 2010 by change to a less thick walled radome of same OD and widening the slot to 11 mm, adding two sub-pF flapper capacitors 7 cm away from the feed point for good SWR with radome on and reducing slot's length by 20 mm on both ends. Now the VSWR is 1/1.27 and the antenna appears no longer to be resonating >70 MHz too low. The slot's cylinder is made of rigid copper tube of 1.5 mm wall thickness with 35 mm OD.  The announced gain of Alford long slot antenna is given as  3...7 dBd, with the vertical pattern developing strong side lobes at upper end of operating frequency range and loosing gain. My estimate of OH5SHF's slot antenna's gain is now around 3 to 5 dBd and yes, it would still work slightly better on lower part of the 23 cm band. Must be related to cavity's tube diameter - no gimmick changes that.

The 2320 MHz radome is a 1 m long 110 mm Uponal PP pipe with end-caps and galvanized clamps bolted with stainless steel side-mounting supports. The antenna inside the radome is a re-scaled YU1AW-designed H-polarized sector antenna called Quados 8 originally for WLAN consisting of 8 stacked spaced quad loops fed with open-line. SWR is 1:1.4. The feeder coaxial is 1.3 m of RG-223. The front-side alumininum foil laminated reflector plane consists of  760 mm by 103 mm 12 mm thick plywood film veneer. Adhesives used were Poylurethane glue (Alum. foil laminating on plywood and coax through hole) and hotmelt-glue (element support spacers).

The 2320 MHz beacon's ODU built inside a ABS enclosure, consist of a bias-T with 96 MHz BPF, the *24 multiplier, 3-section 2320 MHz interdigital BPF and a 1 W WiMo ATV PA (modified for CW BCN use) added with home-made 2-section low-pass filter and a harmonic stub. The antenna illuminates a  +-35°-wide (-3 dB points) (+-57° at -10 dB) sector with about 25 W ERP from S to W to NW centered at QTF 240° towards OH2- and further out - propagation condtions permitting. Reception in the back-side of the antenna panel is limited by the low ERP of approximately 1 W to sectors N, E to SE and even less by immediate structural obstacle blocking NW to N sector. Reception is possible at shorter ranges by reflections from nearby structures located in the main-lobe.

OH5SHF 432 MHz: home-made (in PA) synthesized uC-controlled 50-mW exiter-TX with C-MAC (IQTCXO-250 HP +-2.5 PPM 0...+50 °C) TCXO time/frequency-base and embedded keyer and RF PA with Mitsubishi M57716 hybrid on 432 MHz followed by 6-stage helical filter and a cavity band-pass filter.

OH5SHF 1296 MHz:  home-made transmitter with 108 MHz with thermostat (QH40A) heated (TC)XO (temp. drift: see graph below) and multiplier chain of OH4KHH-design (s.k.) with BFR90 transistors followed by 2-stage MMIC amplifier with +11...+19 dBm output driving a Mitsubishi M67715 hybrid, which drives the M57762 hybrid RF PA with 2-section pi-LPF followed by a cavity BPF. 1296 MHz keying is generated by a 27256-EPROM-based keyer circuit inside 1296 MHz multiplier&exciter.

1296 MHz transmitter uses A1A keying with a message loop containing call sign, locator. On 1296 , a long carrier, but on 432 MHz a series of dits with 2 second gaps. Enclosure's and 23 cm TX multiplier&driver cavity's resonances are damped with fins of black ESD adsorber foam.

The 13 cm TX (a bias-T, 96 MHZ BPF followed by G8ACE multiplier + 3-pole interdigital BPF and 1 W WiMo PA w. LPF) are installed inside the outdoor enclosure.
The 96 MHz keyed drive comes just as on 10 GHz TX, downstairs from QH40A heated DG8SAQ USB synthetizer followed by PIC-keyed ERA-5SM amplifier with double 96 MHz LPF at input and 96 MHz LPF and HPF at output (and the bias-T), delivers +8 dBm (and +14 V dc) to 30 m of RG-58 running up to the tower top ODU shown above. The keying is A1A and consits of callsign, locator and a 90 s long carrier.


The 432 MHz Phelps/Dodge ex. duplexer + cavity resonator's pass-band responce (wide and narrow sweeps)

1296 MHz cavity BPF

 3 GHz span sweep through 30 dB att., no spurious signals above -75 dBc noise floor

3 MHz sweep of 432 TX and 1 MHz sweep of 1296 TX.
432 MHz beacon's in-band spurious signals (3rd harmonic mixing with 1296 MHz signal) are -81 dBc (lower) and -88 dBc (upper)
or better. Key-up power output is -70 dBc (1 uW out).

0...3 GHz sweep of 2.3 GHz band TX


2.32 GHz 8-loop spaced Quad stack with +-8° vertical and +-35° horizontal HPBW.

The OH5SHF 10368.935 MHz beacon uses A1A keying with RF-power output of 0.5 W to horizontally polarized omnidirectional waveguide slot antenna yielding 4 W of ERP.

Mechanical difficulties in adjusting and temperature-aging  issues with ordinary XO oscillators caused the need to find an easier-to-adjust oscillator. The Si-570 LVDS 20 ppm version was the only one available, but with serious doubts about the temperature stabilty, while it's QRG is easily adjusted with USB cable and a laptop PC. After aging for 2 months the SDR-Kits unit and increasing Si-570 chip's temperature to +40 °C, the drift from changes of ambient temperature reduced to a fraction of what it was unheated.

The DG8SAQ Si-570- based USB synthesizer generates 108 MHz. This unit is located indoors in a partially insulated enclosure having inside a constant +35 °C(+- 1 °C) temperature for stability, while the Si-570 is heated to +40 °C with QH40A heater chip. This "double ovening" procedure achieves +-2.5 kHz stability at 10 GHz with IDU room temperature varying between +10 to +20 °C. Without heater and oven, the drift would be tens of kHz +- on 10 GHz. The equipment room's ventilation was fitted with a thermostat controlled fan in June 2011 and this should prevent thermal frequency run-away instabilities in the future during extremely hot summmer weeks. The synthesizer's output is low-pass filtered, boosted to +18 dBm with a keyed ERA5SM MMIC amplifier stage, filterd with 108 MHz LPF and BPF. The +14 dBm 108 MHz drive is fed to ODU via 35 m of CATV75 coaxial cable. The keying with message: "OH5SHF  KP30HV and a long carrier is cycled every 1 minute, is generated by a G4JNT RS232- programmable PIC-keyer installed by the Si-570 synthesizer.

The 10 GHz outdoor unit, partially sponsored by OH5AG, includes 108 MHz input BPF, DB6NT's MKU10G beacon unit with multiplier stages from 108 MHz to 10.368 GHz. The 10 GHz 200 mW output from a flanged  MGF1801-special drives RATS sponsored  FLX202MH GaAs-FET power amplifier producing about 0.5 W RF-output to a RATS sponsored 9dBd omni waveguide slot antenna at 144 m ASL with free take-off. Relative RF output power level is indicated with a LED-bar display located on the bottom of outer ODU enclosure. However, the indication depends strongly on ambient temperature since the PA RF couplers's diode is not temperature compensated. The outer polycarbonate enclosure is EMC screened with spray and EMC-gasket material (cavity RF adsorber foam sheet and ferrite sleeves on cables). It has a top-side mounted antenna radome pipe of Polypropylen sealed with rubber O-ring, MS Polymer and G.P. type hot-melt glue, sprayed over with rim silver spray paint for UV protection. While the Polypropylen material is easy to find and has very good electrical properties at 10 GHz, it is difficult to glue. Only adhesives with Polyolefins (w. PP surface yellow flame treatment) really work with polypropylen. The radome also unfortunately increases the 4 dips on the WG antenna's Az-pattern quite severely, which however is unavoidable and typical.


OH5TEN 28.8000000000 MHz GPS-locked QRP beacon

28.800 MHz BCN

 The PIC keyer is G4JNT design which keys (A1A)  the ERA-5 SM  MMIC in the TX amplifier chain. Mitsubishi RD06HHF1 FET in the PA feeds via 2 dB cable lossses and mid-line LC-match (50 to 71-j20 ohms), some 1.9 W RF to a slanted-dipole with horizontal polarisation at 9 m AGL. The ID "OH5TEN" is send  every 90 seconds. Description of the unit was presented at OH5AG's summer meeting in June 2009 and in July 2009 issue of Radioamatööri-lehti (available at SRAL website in PDF format for SRAL members).

The frequency stability is typically better than 2*10-12 on one minute basis and better for longer periods of time and can be only affected by temporary LOS of adequate number of GPS satellites, which should not occur, or during short periods of high electron content of the ionopshere - typical during strong auroral displays. The other notable benefit is the absolute correctness of the center frequency, which does not rely on any local frequency source prone to unknown offset.

28.8 MHz is in harmonic relationship with 144, 432, 1296 and 10368 MHz ham bands. Within the range of reception (of about 30...50 km), anyone having a 28 MHz horizontal antenna and a receiver, can zero-beat his own signal source (HF rig's TX or signal generator) against OH5TEN 28.8 MHz beacon and by using their own TX's signal's harmonics, get accurate frequency signal for 2 m, 70 cm, 23 cm and 3 cm bands. Since HF rig's harmonics are non-existent above 500 MHz, for 23 cm and 3 cm bands' a comb generator is usually needed - a simple device which creates harmonic signals from low-power RF (ie. 0.5 mW), which can be fed to U/SHF- receiver directly with a cable or RF-coupler. This comb generator can be fed on 28.8 MHz with signal generator or from HF TX via ~ 45 dB power attenuator of sufficient power handling capability.

OH5TEN's 28.8 MHz  beacon's ground wave coverage. Computed signal strengths (S-units) as received with a 6 dBd antenna at 25 m AGL.

Radioclub of Kouvola (Kouvolan Radiokerho ry.), OH5AG is the license holder of  OH5SHF, OH5TEN and OH5RBG.

I would like to thank Ari, OH5KFP and Aki, OH5MWZ for their help re-installing the OH5SHF beacons, it's antennas and OH5RAC's antennas and our radio club OH5AG for sponsoring crystals&synthesizers for all of the beacons from 10 meters to 3 cm and of course RATS ry for sponsoring two 1 W microwave PA's and the 10 GHz slotted WG antenna.

OH5RAC 145 MHz FM repeater's mobile coverage with different mobile (green 10 W, blue 50 W) & portable (yellow) equipment.
The repeater has been accessed 7000 times / year. TX and RX frequencies were adjusted in April 2006: deviation  <200 Hz from nominal.

Non-ionospheric path F-S measurement data of OH5SHF,  OH5TEN and OH5RBG beacons, June 2004...Dec. 2013:

QRB: 10 m @ max gain lobe
28.2285 MHz
50 MHz
432 MHz
1296 MHz
2320 MHz
+25 dBm
+28.7 dBm
+10 dBm
-14.5 dBm
-20 dBm
0 dBd, 0 dB
0 dBd, 0.1 dB
4 dBd, 0.4 dB
-2.5 dBd, 0.8 dB
-1.5 dBd, 1.5 dB
2.5 m
2.5 m
2.5 m
2.5 m
2 m
OH5IY   2.1 km  236 deg. measured Prx (@input) Ga , line loss hant
28.2285 MHz -41.6 dBm (250°, VHF arr:280°) +0 dBd, 1.0 dB 9 m
28.8 MHz @ QRB 10 m +8.4 dBm (w. 1.9W) (85°, VHF arr:180°) +0 dBd, 1.0 dB 9 m
50 MHz (equalized(T&R): +3 dB) -31.4 dBm (50°, VHF arr:185°) +7.0 dBd, 1.0 dB 9 m
70 MHz  -55.6 dBm +2.5 dBd, 2.5 dB 10 m
432 MHz
(@ TX cable PA TX input)
-39.6 dBm (peak-forest fading). Sept. 2010 -43.1 dBm (rain) Oct. 2010 -40.5 dBm +24 dBd, 2.6 dB 19 m
1296 MHz
(@ converter's RX input)
Horn antenna's output
-54.6 dBm (11-2010)
-56.4 dBm (06-2012)
-82 dBm
+16.2 dBd, +27 dB, -14 dB

+5 dBd, 0 dB

19 m

2 m

2320 MHz -86.1 dBm (30-4-2011)
-89.7 dBm (8-6-2012)
-87.6 dBm (12-7-2012)
-86.5 Bm (30. Apr. 2011)
-86.9 dBm (30. Apr. 2011)
+10.1 dBd horn, 0 dB
+10.1 dBd horn, 0 dB
+10.1 dBd horn, 0 dB
+10.2 dBd panel, 0 dB
+9.6 dBd panel, 0 dB
2 m
2 m
2 m
2 m
OH5IY/4   57 km  7 deg.
28.2285 MHz -85.7 dBm +5.5 dBd, 1.5 dB  13 m
50 MHz -75.4 dBm +7 dBd, 1.2 dB 15 m
OH5WD(Jaala) 17 km 350 deg.
28.2285 MHz -64 dBm +5.5 dBd, 0.8 dB 15 m
50 MHz  -67 dBm +4.5 dBd, 1.1 dB 15 m
OH5WD 1.7 km 170 deg.
28.2285 MHz  -38.1 dBm +5.5 dBd, 1.4 dB 5 m
50 MHz -37.0 dBm  +4.5 dBd, 0.9 dB 5 m 
OH5LAQ 10 km 195 deg.
28.2285 MHz -41.4 dBm +9.4 dBd, 1.5 dB 26 m
50 MHz (+4 dB) -38.2 dBm  +8.7 dBd, 2.1 dB 21 m
OH4KOP 57 km 5 deg.
28.2285 MHz -80.2 dBm +7.0 dBd, 1.3 dB 25 m
50 MHz
Note:  RX power indoors with a 5.2 dBd / 10 dBd wide-band horn was -71 dBm on 1296 MHz and -85 dBm on 2320 MHz on 2. Oct. 2010 (-79 dBm on a very cold winter day).


50 and 432 MHz beacons were 7 dB above the noise level with 2.4 kHz B.W. and 2*6-el.  (CC 6176B) & 2*19-el. (CC 719B) Yagis 30 m AGL w. mast-head SP-7000 preamp in KP31PU.
OH5ADB received in KP30HV on 144.455 827 MHz with 19.7 dBd antenna and 1.4 dB feed losses at -117 dBm.

Copyright 2004...2014  OH5IY, the beacon keeper