I brought the K3 (#722) to work today once again, this time to check the FM operation of the radio. I had calibrated the oscillator a couple of weeks ago, and it has only drifted 16Hz since then! Measurements taken on the same equipment, same freq standard Motorola 2670, Spectracom 8195A. My FM measurements were as follows: Frequency was 52.525, did not check 10 meters. 12Db SINAD .47uV -113.4dBm Looses squelch (13) takes .79uV -109.0dBm to break Squelch closes at .33uV -116.5dBm Max modulation acceptance 4.90kHz TX CTCSS deviation .3kHz (at 114.8Hz) Maximum mic deviation 2.0kHz (at 1000 Hz mod frequency) Max overall deviation 2.29kHz (above two tones)
Here are the issues. The TX deviation and RX mod acceptance are for narrowband operations. We need the CTCSS to be around .6kHz deviation and mic audio around 4.2kHz or so. Maximum overall deviation should not exceed 5kHz. In the US we are still "wideband" on these frequencies, in both commercial and amateur service, emission designator 20KOF3E. We need more deviation to sound good here in the US. That said, the recovered TX audio waveform looks great! With mic gain turned up all the way with the Elecraft mic, there was no distortion at all on the mod scope. Looked really nice, better than a $14k Motorola Quantar. Very nice modulation. It also simply takes too much signal to break squelch. Loose squelch should be able to break below the 12dB SINAD point. So, please more TX audio, or a way to select wide/narrow if narrow is needed elsewhere in the world, and better squelch action. So, for now, still on the MASTR II for 6 meters... 73 Josh K6ZRX _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
