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Author Topic: Kenwood TS-440AT/Astron RS-35M  (Read 1308 times)
KD2FAH
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« on: January 09, 2003, 10:33:04 PM »

I recently purchased a used Kenwood TS-440AT and a new Astron RS-35M. I am using a 10-meter 1/2-wave dipole antenna and I have been TX/RX only a frequencies within that band capable of being serviced by that antenna. I have a few questions: the first is on the Astron. When the rig is powered up TX or RX I am reading solid 14 volts on the meter and drawing a couple of amps. When I transmit volts holds steady at 14 and the amps don't jump beyond 12 amps on the meter. On transmitting I expected to draw quite a few more amps. I thought I would draw up to 30amps. My signal reports back so far report some distortion. Is it possible that there might be a problem with the power supply? To compound the problem I am thinking my 1/2-wave dipole cut for 10 meters can be the problem, is it possible that it is having a problem with the AT feature on the 440? I did hook-up my old HTX-100 to the Astron and transmitted and made good contacts with good signal reports, amps drawn was a little less than 10 on the meter which is what I thought was right for the HTX.
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AC5E
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« Reply #1 on: January 09, 2003, 10:44:58 PM »

HI: Trying to diagnose a rig problem at this distance is tricky but it sounds very much as though your rig is "folding back" its power output. The problem may be high SWR, RF "in the shack," or some other problem.

Power consumption on transmit should be around 20-21-22 amps, 13 amps is an indication something isn't right. It quite possibly could be an AutoTuner problem.

But your comment about distorted audio leads me to consider RF in the shack to be the primary suspect. This happens when your feedline is a better match to the outside of its shield than to your antenna. And it can cause all sorts of problems.

Let me suggest a trip to www.radioworks.com and a look at their line of "current baluns." These force the RF to stay at the antenna, instead of becoming an uninvited guest in the shack.

73  Pete Allen  AC5E
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K6AER
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« Reply #2 on: January 09, 2003, 11:59:22 PM »

While it is possible you have RF getting into the microphone circuit via the microphone or cord you should not take one off-the-air report as gospel. Along as the antenna is more than 30 feet away from a 100-watt radio, the microphone cable is properly shielded you should not have a RF ingress problem Many hams will have interference on their receivers or their set improperly adjusted and not realize it. Bottom line result is they report your audio distorted or their RF gain may be set to high.

Your description of the amperage jumping to 12 amps is normal for 100 watts of sideband operation. The Duty cycle of SSB audio is about 12-15 % as compared to a constant CW carrier. A CW carrier should register about 18-20 amps for a constant carrier with 100 watts out. Some older solid-state transceivers will read higher amperage than the above figures. Also the amp meters on most power supplies and especially the Astron series can be off by as much 15%.

All of that said, find someone that lives close to you to evaluate and listen to your off air audio. That way the atmospheric and QRM variables are at a minimum. As for the power output most current transceivers operate at about 35% efficiency. To calculate your expected current draw, take your RF power output read in watts and divide by .35, take that number and divide by 14 which will give you the approximate amps in the continuous carrier mode. Current draw while transmitting is best measured in the continuous carrier mode. Your SSB peak carrier power and CW power will be the same on a solid-state radio.

Good Luck,

Mike - K6AER
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WA9SVD
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« Reply #3 on: January 10, 2003, 12:48:25 AM »

The 14 Volt reading is within tolerance; the meter may not be perfectly accurate and you may want to check the actual voltage with a more accurate multimeter.  Also, the current draw from your radio would be on voice peaks, and the meter in the power supply can't respond that fast.
    More importantly, you may have the Microphone gain set WAY too high, causing the ALC circuit to kick in big time; this could very well be the cause of your reports of distortion!

    Contrary to the instructions in the printed manual, you do NOT want to run the mic gain into the ALC region.  Actually, you want to see an ALC reading ONLY on the highest voice peaks!  The reason is that once you get into the ALC region, you are already in an area where you may be overdriving the final amp. and the ALC action is in response to that overdrive.  Watch your power output, and back off the MIC gain.  You will still see the power output is there, even when only your highest voice peaks show a small ALC indication.  If you are continually showing an ALC indication on your meter, you are most likely overdriving the output of your radio, and very likely causing splatter and a wider signal than necessary.  Remember, if the ALC indication EVER goes into the red, you are probably exceeding the ALC level and creating a wider than necessary signal.  And the ALC meters can't follow the voice peaks either, so if you are near the ALC peak or EVER see the indicator go above the ALC region, (or into the red for some meters) you have already overdriven the output and are creating distortion and splatter.
    Good luck with the rig, and try to get a local friend to help you set things right, and everyone will be happy.  I think your system is functioning normally.
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KD2FAH
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« Reply #4 on: January 10, 2003, 09:30:32 AM »

OK. I will try MIC gain adjustment and take it out of the ALC region. I do agree the other problem could possible be high SWR. I was told that an auto-tuner will not work properly with a dipole and will have a problem tuning. However, I assumed if I turned off the auto-tuner and set the auto/thru to thru I would by-pass the auto-tuner. Since I am using a 10 meter dipole and trying to broadcast in the band I would think I'd experience good results. Finally running my old HTX-100 through the new Astron and the dipole does yield good results. Any comments appreciated.
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KD2FAH
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« Reply #5 on: January 10, 2003, 09:37:38 AM »

Local report from a station about 7 miles away reported low audio and some distortion when using the Kenwood. When using the HTX-100 my report was little distortion, if any, but still a low audio. Rigs are properly grounded and antenna is approximately 50 feet away.
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WB2WIK
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« Reply #6 on: January 10, 2003, 12:06:28 PM »

Your TS-440SAT may have a problem, but I wouldn't jump to that conclusion.

As stated before, you cannot go by the Astron's "ammeter" reading, at all, when using a rig in SSB.  When you go to RTTY, with the CARRIER level turned all the way up, and a good load (antenna match), the current drawn by the TS-440SAT should be about 20 amps.  It should *never* be as high as 30A, that would indicate something definitely wrong.

The "14V" meter reading may be off, or you might have too much voltage drop in your power supply cable between the Astron and the Kenwood -- or both.  Use a DVM if possible to confirm the Astron's reading, and then use the DVM with pinpoint probes to measure the voltage *at the Kenwood's power connector* on the rear of its chassis, when you are actually transmitting full power.  The TS-440SAT wants to see at least 13Vdc at its power connector -- it doesn't matter a lot what the Astron voltage is.

In my experience, the Astrons usually need to be cranked up to at least 14V, if not a tad more, to sufficiently supply power to most 100W rigs having a power cord more than six feet long and having in-line power fuses, both of which have voltage drop at 20 amps.

If your issue has nothing to do with power at all, you may need to investigate whether you've got a broken ground connection in the Kenwood mike or its cord or plug -- this is an extremely common problem, and can cause distortion.  If possible, try another mike.

Of course you should *never* modulate the Kenwood so that its ALC meter reading goes above the "ALC" indication, and in general, it's usually poor practice to advance the mike gain any further than that which just starts to wiggle the ALC meter a little bit.

On SSB, there's really no such thing as "low audio," although that's a common report.  Usually, it means the peak-to-average ratio is too high, e.g., your occasional voice peak is okay, but your average talk power is very low.  This can be an ALC problem, or just your voice characteristics, or maybe your speech compressor isn't turned on or working properly.

WB2WIK/6



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RobertKoernerExAE7G
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« Reply #7 on: January 10, 2003, 02:17:00 PM »

“Local report from a station about 7 miles away reported low audio and some distortion when using the Kenwood. When using the HTX-100 my report was little distortion, if any, but still a low audio.”

You are using a dipole on 10.  It probably has the classic figure 8 pattern, major lobes east and west when the antenna runs north and south.

If the local station you talked to has a vertical, your signal will be “weaker” to him.  If his station is vertical and off one of the ends of your antenna, you’ll be even weaker to him.  None of that has to do with mic gain.

There isn’t any reason your tuner won’t work on 10 meters into a 10 meter dipole.  My tuner, MB-V-A has some problems on 10 meters, but functions fine.  Since the VSWR is low on my triband antenna, I bypass my tuner.  However, I do use the built in tuner in my rig, which works fine on all bands.

Bob
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