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"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.

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.

 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.

OH5ADB received in KP30HV on 144.455 827 MHz with 19.7 dBd antenna and 1.4 dB feed losses at -117 dBm.