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Author Topic: FT-1000MP Vs TL-922  (Read 529 times)
VK2CNN
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Posts: 38




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« on: January 16, 2001, 06:31:36 AM »

Hi everyone,

I have FT-1000MP hooked up to a TL-922. Quite often I hear people saying that my audio is distorted. If I don't use TL-922, I am told that I have good audio. I only use about 50w exciter input, and certainly not overdriving TL-922. It seems that there is some sort of feedback from TL-922 into FT-1000MP, and I am not quite sure how to tackle this problem. Is there anyone out there who can help me through this problem ? Any help would be appreciated.
Thanks in advance.

Geoff
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K1IR
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Posts: 11




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« Reply #1 on: January 16, 2001, 10:14:55 AM »

Geoff,

I own the same setup, and have had it working just fine. I suspect that your problem is related to RF interference to the 1000MP resulting from running higher power.

Do you feel any RF burns if you touch the mic connector of the FT1000MP when you are transmitting? This would be a sure sign that you're getting RF back into the transmit audio circuits.

What kind of antenna are you using, and how far is it from the equipment room? If it is close to the room and/or you have a high swr, you are very likely to be getting radiation back into the shack.

Is all your equipment properly grounded? Are you sure? Try removing the ground connection and see if the problem gets worse or better. If it gets worse, look into an even better ground, and look into other places where the radiation might be coming into the system. If it gets better when you disconnect the ground, it means your ground is probably acting more like an antenna or creating a return loop for the RF. You may need to improve your ground connection.

To find out where the RF is coming in, try disconnecting every accessory from your setup. Just run the rig to the amp to the antenna. Remove antenna switches, keyers, headphones, external speakers, computer connections, etc. If the problem remains, consider the possiblity that your RF is entering through ground or through the ac power line. If it is gone, start putting all your accessories back into the setup one by one. Eventually, you'll find the culprit.

Hope these ideas help!

73,

Jim K1IR
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K1IR
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Posts: 11




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« Reply #2 on: January 16, 2001, 10:31:54 AM »

There is also a small chance that the TL922 has a problem. Make sure you are tuned up properly. Try the amp at a friend's shack. But, I don't think you'll find that the amp is functioning improperly.
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WT8Y
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Posts: 65




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« Reply #3 on: January 16, 2001, 10:32:21 AM »

You should be able to hear the distortion in the monitor mode on the 1000MP. This is a common problem
at higher power levels, also suggest you stay away from end-feeding wire antennas. Good RF grounding
usually takes care of these problems. Does this only happen on one or two bands, sometime a change in feedline length will help and or a coax/ferrite choke on the feedline..
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VK2CNN
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Posts: 38




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« Reply #4 on: January 17, 2001, 05:57:32 AM »

Thank you everyone for your contributions. Your contributions were very much appreciated. Today, I have tried a few different things to try to eliminate or reduce RF feedback or audio distortion.
I tried to turn processor or compressor off and reduce Mic gain to about 9 O.clock position on FT-1000MP. I also set RF power to maximum on FT-1000MP. The result is that there was no distortion in my audio. However, my external power meter shows about 350 watts on voice peak. That is with 100 watts input to TL-922 only getting about 350 watts out. Is this normal or abnormal ?. Any suggestions ?. Please let me know your Mic gain setting and whether it really is necessary to turn processor off. In the mean time, I will try to look into your contributions and investigate further.
Thank you once again for your help.

Cheers.
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KA2QFX
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« Reply #5 on: January 17, 2001, 03:24:57 PM »

I'm surprised nobody mentioned this but... Unless you have a scope, or peak reading meters, you are estimating your driving power with an average reading meter. DEpending on your voice characteristics this could give you as much as a 3:1 difference in peaks and average. It is possible that your peaks are overdriving the amp a bit. To be sure you don't overdrive the amp, have you run the ALC output from the amp back to your exciter? You might be very surprised that your ALC will kick up and reduce your drive indicating that you were in fact overdriving the amp. Besides, it's just good practice to do this.  
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VK2CNN
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Posts: 38




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« Reply #6 on: January 18, 2001, 06:06:45 AM »

Once again thank you to all.
I tried a few more different things today. I found out the distortion only happens on 15 meter band. No feed back or distortion happen on 20 and 10 meter bands. I must tell you that I was using desktop mic Yaesu MD-100 with FT-1000MP. When I tried with handheld mic Yaesu MH-31, to my surprise, I did not get any feedback or distortion in my audio. Reports from other DX stations were good. For the time being, I will be using handheld mic until the problem with desktop mic can be solved. Any solutions or ideas from technically minded hams out there ?
Thank you.

Cheers
VK2CNN
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KA2QFX
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« Reply #7 on: January 18, 2001, 02:37:59 PM »

Well, it sounds like you've identified the problem farily well.  There's lots of methods written to alleviate RF in a mic. Most deal with some sort of L network in the audio lead inside the mic. A small value or resistance in series and a bypass cap to ground on the mic side, about .001uF is pretty common. I like adding a ferrite bead, or a snap-on choke over the mic cable. The effectivness of any solution really depends on the amount of RF you're getting in the shack. The best way obviously is get rid of the RF if you can.
I still reccomend hooking up that ALC line though. The added gain of the amp in a closed loop often gives you a little more audio compresion too, can't hurt. Given that FT-1000 is capable of generating 200W I wouldn't be surprised if you peaks a over what the amp should really be hit with. Hope you resolve it, good luck.
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LA4WKA
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« Reply #8 on: February 23, 2003, 06:20:05 PM »

Hi.
I also use ft-1000mp mk v field and tl-922.

Never use compressor in the amplifier, as one said: little crap in -> lots of crap out:-)

Also look what setting the menu 4-4 is at, I like the off setting, using hail sets, it gives clean audio.

And if you feed the 922 with 100 watts, you should get WAY more then 3-400 out, check antenna, bandswitch for right band, and never argu with the manual, the meters shall be within the limits, max 200mA IG 600-650mA IP, this gives me from 1200 to 1500 watts out SSB, about 800 CW, depending on band and antenna...and please remember, NO CW IN SSB position.. Have fun
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