The AM Forum

I have a IC-718 with a Heil mic on the air. I'm looking for someone to comment on my audio. I'm going to try join the QSO in progress on 3.885.

Bottom line is simple, unmodified rice box audio is tough.
They are designed to lop off everything below 300Hz and above 3000Hz., broadly speaking. Without mods most commercial solid state SSB intended radios do not sound very good. Mine included (a slightly modified TS-440s)!

Since you have to set ur carrier to about 20-25% of rated CW carrier level, that puts the typical rice box down into the 10-25w carrier level, very weak. If you are going to try to do that you definitely need a good antenna to have a prayer of being heard.

The "standard" for AM QSOs "back in the day" was a pair of 6146s modulated fully, which translates to a >100watt carrier with 200-400watts PEP after modulation. Consider that a Ranger or a ricebox run into a pair of 3-500s (in a linear) will give you only slightly more output than that (maybe), and you start to see the scope and nature of the issue?

That was for your everyday signal - the same as today's Kenwood or Icom, Yaseu SSB signal. The "big boys" - they guys who got heard were running 400-1000watt plate dissapation tubes that were then plate modulated! Same thing today.

Bottom line is that although it doesn't seem like it, an old vintage transmitter does more than seems obvious at first look on AM!  ;D

Consider maximizing ur antenna and maybe finding a vintage bit of transmitter or some other similar output level transmitter?

Personally, I think a good part of the fun in AM is the really kewl gear.
That and keeping the shack warm in the cooler months.

           _-_-bear

AIn't nothing wrong with running a stock ricebox on AM.  But as Bear said the audio is definitely shaped for SSB service.

SOmetimes there's a phone patch input on the back that bypasses all the audio filtering, and if the crystal filter inside the radio is bypassed (either by modification or by design of the radio) they are capable of FB audio.

I would bet you could get much lower distortion out of a balanced modulator (as in a SSB rig) than from plate modulation; plus they don't produce splatter on downward peaks AND they're capable of impressive upward peaks.

I've modified several Heathkit toob SSB rigs for hifi AM and they work quite well.  Still, with the pair of 6146s in linear service, they're only good for about 25 watts out.

Most of the current crop of imported rigs now run great sounding low-level modulation in the AM mode. Also, a number of rigs now use DSP's in their mode generating areas. As in the case of current Icom rigs, there are no crystal filters. In the PRO series, there is no balanced modulator. Also in the PRO series, audio response can be tailored down to about 100 Hz and well above 3000 KHz. Also, typical AM bandwidth for these rigs is about 5.9 KHz. Most of the current Yaesu rigs (except pseudo mobile or sandwich size rigs) are tailored for great sounding AM. Kenwood TS-2000, TS-870, and TS-850 are great rigs with great sounding AM.  Some of these rigs have provisions for connection to the audio chain beyond the front end audio and compressor circuitry. Great feature to have if you decide to connect external processing. On many of these current imported rigs, no modification is necessary to sound great on AM.

Many older imported rigs from 10 to 20 years ago, especially the ones that were designed for mobile use, were very marginal on AM unless internal modifications and/or lots of diddling was done to make them sound "decent".

Bottom Line is:

  RUN WHAT YA BRUNG!! don't woorry bout nothin!!
Have fun and worry bout making HI-FI with a real radio later!

73 Brent W1IA

I agree.  I just finally got on the air with an unmodified Gonset G-76.  I will probably mod it later for better audio, but for now what I have been told is rather comm quality audio is punchin' through quite well.  With only 25W carrier from it I am sure it helps me get heard at that power level.  And I've been heard even with all of the static crashes going on last night.  Get it on the air.  Worry about making it perfect later.

 is that what you have Dave? last G76 i worked on put out a lot more than 25 watts. try to get ahold of Frank KB3AHE. he's the high matser of the G76. sorry we did not here you that well last night. as to the guy with eh IC-718 and Heil mic- i have heard a few of those on AM and they sounded quite good. they drive a linear very well on AM too. i'm considering using one for my return to HF mobile. Brent got it right- run what ya brung, and put up a big mo-fo amtemma if you can. low power requires a great antenna to pull it off on AM.

The one I had put out something like 50 watts, IIRC.

..jeff, ve3mte has the icom ic707..similar rig...25 watts to a 350' loop, open wire fed...audio is very good, and he is herd far and wide, due to the antenna...my yaesu ft847 sucks on am transmit...receive is gud, but is by far the worst rig fer am....
  3885 can be pretty tough..alot of qwarm, etc...try down lower...our bunch hang out on 3725, and there are guys on 3730/33, 3715/05....alot quieter, and i frequently werk guys there with 25 watts....tim...sk...

refer to the attached table.
 Audio into the acc. socket goes pin11 (audio) pin 2(gnd).
AF detector output appears on pin 12.

On AM the normal filter selection is 6KCs both trans. and rcve.
Narrow selection is 2.3 KCs