Radio RF Performance

Contents:

Here we lay out how performance will be measured and how it will be presented.

Equipment Used:

• Marconi 2955 radio test set (measures transmit output power and recieve sensitivity)

• Coaxial Patch Lead

• Required RF adaptors for specific radio

• Audio patch leads for specific radio

• Bench power supply

RX Test Procedure:

• Connect coaxial patch lead between radio RF and radio test set RF connectors

• Connect audio patch lead between radio AF and radio test set AF connectors

• Set radio test set to RX Test
  Enter radio RX frequency
  Set carrier output signal to 0.2μV
  Set modulation to 1KHz tone
  Activate SINAD display

• Observe SINAD display and increase carrier output signal until SINAD is (usually) 12dB

• Observe the carrier output signal required to achieve 12dB SINAD

TX Test Procedure:

• Power radio from bench power supply

• Connect coaxial patch lead between radio RF and radio test set RF connectors

• Connect audio patch lead between radio AF and radio test set AF connectors

• Set radio test set to TX Test
  Enter radio TX frequency
  Set modulation to 1KHz tone
  Activate SINAD display

• Observe SINAD display and AF Frequency

• Observe output power

~Yaesu FT60 - Test Results

These are the preliminary test results which prompted me to proceed along this path.
The test results were gained using a somewhat quick and dirty method, where the radio was connected to the radio test set via RF only, the squelch was set such that the radio speaker was only just silent, and radio test set output power was slowly wound up until the radio squelch "broke". This is not the formally accepted test for receive sensitivity, but gives some idea how the radio performs.
The specific radio under test has been wideband modified, so will transmit outside of the amateur radio VHF/UHF bands.
Be careful how you read the graphs - Sensitivity is scaled in μV and this is a measure of how much voltage it takes to break the radio squelch, unmuting the speaker. Less voltage = higher receive sensitivity. 

~Yaesu FT60 - Conclusion

Bearing in mind that the above test results were attained using a quick and dirty method, the results are quite interesting.

In the VHF band, sensitivity starts at around 0.40μV @ 137MHz which is double the voltage required to get most commercial radios to open the squelch (most open at around 0.2μV).
The sensitivity gradually gets slightly better towards 144MHz but still hovers in the mid to high 0.35μV region.
Suddenly, at around 150MHz, the sensitivity drops off a cliff to 0.53μV and continues to drop right up to 160MHz.

In the UHF band, sensitivity starts at around 0.39μV @ 420MHz and then displays a pleasant, well behaved curve throughout the 430-440MHz band at around 0.35μV - This is still worse than the 0.20μV that most commercial radios achieve.
Sensitivity drops around the PMR446 band to 0.37μV and, again, drops off a cliff at 453MHz dropping to 0.49μV. From 453MHz onward, the sensitivity continues to get worse.

It is obvious from these results why my FT60 has performed worse  in the commercial bands than than a beat up old GP340. The FT60 clearly has low pass filters above the amateur radio bands (144-146MHz & 430-440MHz).

This radio has been with me for well over 10 years, and has tolerated the most atrocious treatment. Despite this, I could wipe it down with a spray of furniture cleaner and sell it as "new old stock". Not a single thing is broken or worn out.
During the test, I was using an aftermarket battery, which seems to hold a charge even under heavy use, but this is yet another violation of good testing practise - a bench power supply should be used to eliminate the effects of the battery going flat during the test.

Overall Conclusions:

• Radio receive sensitivity is worse than a commercial radio in the commercial bands

• Radio receive sensitivity is worse than a commercial radio in the amateur bands

• Radio MAY perform better than a commercial radio in the amateur bands in an RF rich environment (low pass filters block commercial bands)

• Quick and dirty test routine has gleaned results that have now prompted more robust testing of this and other radios

• Radio performance is significantly worse than the Yaesu specification given in the service manual

Test Improvements:

• Perform all future tests with radio powered from a bench power supply monitored by a calibrated volt meter

• Conduct receive sensitivity test according to 12dB SINAD standard

• Conduct adjacent channel rejection test

• Conduct transmit test including output power, bandwidth, SINAD, harmonic emissions

• Perform a full alignment according to the Yaesu service manual.

• Repeat above tests to verify the effect of alignment

Most radios have some kind of signal meter to tell the operator what the incoming signal strength is.
On commercial radios, the reading is normally displayed as RSSI (Received Signal Strength Indication) and is scaled as dBm (decibel milliwatt). Because these are scaled as decibels compared to a milliwatt, the incoming power can be read directly from the display.

Amateur radio equipment tends to have a meter which is scaled as S-units.
At  some point before the 1930s, the standard for signal meters was that 50μV at the reciever input would correspond with S9. The problem with this was that only in the late 1920s, Bell Laboratories had begun work to deduce the best impedence to use for coaxial cable. The result of this work produced the 50Ω standard that communications equipment now follows, but equipment back then lagged somewhat behind this standard. As a result, the above 50μV = S9 scale could not depict input power because the impedence was not a fixed standard.