lagasse@biomed.UUCP (Robert C. Lagasse) (05/21/85)
1). Has anyone but myself noticed the audio tone quality that commercial
mobile FM gear has? Unlike your typical "police scanner" or even
mass-produced FM amateur radios which have a high pitched hiss when you
disable the squelch, commercial sets have a throaty sounding hiss and the
voice quality is always pleasant, not buzzy. I have tried building audio
filters to change the tone for my 2m gear but all I get is muffled audio.
External speakers help a bit but I am convinced that they are doing
something sneaky inside of the commercial stuff.
2). 6 meter questions:
I am young enough to have missed the heyday of 6m popularity. Does
anyone still produce it for hams? Should I build my own or modify a Motrac
or something? How bad were the TVI problems from equipment used strictly
car-to-car in rural areas? What kind of range advantage can I expect
over 2m mobile-to-mobile? All I want are one or two freqs. Were there any
"popular" ones like 146.520 simplex(2m) ?
Bob Lagasse N 1 A L G Mass. Gen. Hosp.ron@brl-tgr.ARPA (Ron Natalie <ron>) (05/21/85)
Before the days of synthesizers people used to swear by commercial equipment. Everything else was JAP-TRAC. As a matter of fact it wasn't until the multi-band synthesized radio (UV-3) came out that most switched around here. I used to have a Micor (which was the top of the Motorola line), nice solid radio (Western Electric used to build telephones like this). I also have a 2m PROGLINE. Tubes, T-Power (WHINE) (Remember "Progress is our most important product"). I never installed it in my new car. It only draws 6 amps on receive, I'd expect my 4 cylender engine would stop if I transmitted. -Ron Anyone want a slightly used 4 channel progline?
jhs%Mitre-Bedford@d3unix.ARPA (05/22/85)
1. (Re: audio quality) I would think that loudspeaker response would be an important part of it, but possibly IF filter response would be another. For transmit audio, the microphone is very important and you can even hear big differences among ham type transmitters. For external speakers, by the way, it's HARD TO BEAT the Radio Shack "CB Extension Speaker" which sells for about $12.95. Add this to even an HT with low audio power output capability, and you can hear radio calls from 30 feet away from your vehicle (if you put the speaker on the roof or something), even beside a busy highway. (I am NOT exaggerating!) This speaker has excellent frequency response shaping for FM voice communications use. As for microphones, buy a Turner or Shure mobile dynamic mic and you can't go wrong. The IF filter is harder to fiddle with. Also, you should be careful, because the "pros" (meaning Motorola) found out early in the game that you DON'T want a nice square-topped filter -- you want a nice stoop-shouldered Gaussian one because its IMPULSE RESPONSE is also stoop shouldered and short in duration so IGNITION NOISE doesn't ring on into the middle of the 21st century as it would with a sharp-edged filter. Maybe you could buy a 455 KHz IF filter from the "Big M" and substitute it for the one in the el cheapo rig. I dunno about audio shaping, but maybe you could analyze the offending ham rig with an FM generator and audio voltmeter and plot its frequency response at various points to see where the loss occurs. 2. Six meters. I am not a 6m user, but I have noticed that the ARRL Repeater Guide lists quite a few 6m repeaters. You might want to look at it for hints and maybe get on some of the repeaters and ask for further information. Good luck! 73, John Sangster, W3IKG jhs at mitre-bedford