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Radiodork
| | Posted on Saturday, June 21, 2003 - 6:18 pm: | 
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Are there any known adjustments or mods to help obtain more satisfactory A.M. performance for this radio? Does anyone know which is the modulation pot? It seems to be adjusted too high, but then clips. It works very well on ssb, but is like most of this type of radio, very lacking on A.M. Thanks. |
Kc0gxz
| | Posted on Sunday, June 22, 2003 - 7:09 pm: |
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Radiodork
The reason that it works very well on SSB is because that is what it was intended for. Most Ham radios were (and still are) made with "LOW LEVEL" modulation.
If you bought it for AM use on the CB band, then you chose poorly. My suggestion to you is to get yourself a 10 meter radio and have it converted to work in 11 meters.
On AM, any 10 meter radio will give you more modulation than you will EVER need. And some of them will even out-power most of the old Ham rigs on AM too. But for SSB operation, now you're talking my language. In that case, you chose wisely.
73s
Jeff, kc0gxz. |
2600
| | Posted on Monday, June 23, 2003 - 12:28 am: |
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Hi RadioDork,
I second the motion. Ever since the move to solid-state ham transceivers, AM mode has gotten to be a 'stepchild' part of the radio. Popular Kenwood transceivers of the late 70s and early 80s did not even include AM, just CW, SSB and FSK.
Enhancing AM performance just won't make the radio sell any better. For that marketing reason, they have no incentive to spend money on the performance of the AM functions. Besides, hams are only allowed 100% modulation, right? A radio that will exceed that, "clip" the audio, and still be understood just won't sell better. Wouldn't be legal to run, right?
I have wondered for over twenty years, since this kind of design 'took over' in ham transceivers, why some sharp engineer didn't work this out. The AM transmit audio is just a waveform, and the modulator is just circuitry. Sure wouldn't be cheap to develop. Besides, the setup would be different for nearly every solid-state transceiver out there. The "low-level" modulator that Jeff refers to is implemented numerous different specific ways. It would have to be worked out separately for each model you wanted to modify.
Much cheaper to just get a radio with a normal high-level modulator, like the "10-meter"/illegal-"export" radios. The people who build those know who buys them, and why. SSB tends to be the "stepchild" function on some of those.
73 |
Highlander
| | Posted on Monday, June 23, 2003 - 7:32 am: |
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That's the best solution for me too, I use the FT-847 set for all modes but AM - for AM CB, I use my Galaxy DX2517 with a switch betwen the two. But you wouldn't need anything so extravagant for the AM side - there are some AM/FM mobiles from Connex/Superstar that are cheap and sound very stout on AM. I've heard that the Maverick A24 is a good choice, or there are some cheap AM mobiles by Midland that would do the trick.
Somebody told me once that if I really wanted to make the Yaesu go on AM, use an amplified d-104 and wire it to the AFSK jack on the back of the radio! I haven't tried it, but I wonder if it would really work or not. I don't know if the 747 has such an input or not. |
Radiodork
| | Posted on Monday, June 23, 2003 - 11:29 am: |
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Thanks KC0GXZ, 2600, and Highlander. I primarly bought it for ssb operation, but I thought that it could probably be set up for better A.M. performance also - like nuteralizing the circuit that limits modulation peaks. I feel that someone has been into it and cranked up the modulation because anymore than about a 9 0'clock setting on the mike gain with the stock mike causes distortion, and I can see on an rms meter that anymore than that will result in a sharp limit on the power meter. By contrast you can run the mike gain wide open in the ssb mode, and I get reports of really good sound this way. I usually use and old 101B or 101EE Yaesu with some audio mods for A.M., but would very much like to enhance the A.M. capability on this little rig. Thanks again for the input. Dork |
Kc0gxz
| | Posted on Monday, June 23, 2003 - 7:06 pm: |
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2600
I just love the way you explain things. I can't seem to put things in (for lack of a better word) "order" the way you do. You have the nak for expression that I wish I had. I just love reading your stuff guy.
Are you by any chance a school teacher?
73s
Jeff, kc0gxz. |
Radiodork
| | Posted on Monday, June 23, 2003 - 11:21 pm: |
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Hey Jeff, if I were I'LL bet that I would not have mispelled "primarily" up there. I am just a radio operator looking to better the A.M. on this old radio and was told by a friend to take a look and ask over here. Thanks. 73 |
Radiodork
| | Posted on Tuesday, June 24, 2003 - 5:52 am: |
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Sorry Kc0gxz, you were addressing 2600, that makes more sence, I wasn't paying attention. |
2600
| | Posted on Thursday, June 26, 2003 - 12:06 am: |
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Thanks for the fan mail, Jeff.
Never felt rich enough to teach school. Passed the test for Vocational Ed teacher 13 or 14 years ago, but never took the job. I have done programming and design work and run a repair shop, specializing in ham and CB stuff, but I don't solicit long-distance repair work at all. When they no longer carry enough work in the door to keep me backlogged, I might have to change my tune on that one, but not any time soon.
If you like, pop me an e-mail and I'll send links to my (few) web pages. You might be amused.
73 |
Radiodork
| | Posted on Monday, July 21, 2003 - 12:11 am: |
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I don't know what was done, but a ham radio tech has modified the 747 for me and it does very well in the AM mode now,with reports coming in of excellent audio. It must have been very simple because he only charged me $40.00 for the work. So much for the "can't be done" stuff. Dork |
Kc0gxz
| | Posted on Monday, July 21, 2003 - 1:14 pm: |
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Radiodork
There are many converted 10 meter radios that will out-talk the 747 on AM no matter what you do to it.
And no one claimed that more audio couldn't be extracted from it. We're just wondering why anyone would take a fine radio like the Yaesu 747 and turn it into a AM CB.
Jeff, kc0gxz. |
Radiodork
| | Posted on Tuesday, July 22, 2003 - 10:44 am: |
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Who is using it for CB? As for SSB, the performance is the same. I have tried several of the so called 10 meter radios, and do not like them, and usually don't like to listen to them as well. Thanks for the input though. |
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