Author Topic: New installation - TX problem - RX brilliant  (Read 4054 times)

G3UEG

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New installation - TX problem - RX brilliant
« on: 2010-06-17, 16:44:42 »
I set up my remote station yesterday, and after sorting a few computer and network set-up issues,  it was working fine on receive.  I am using the Webswitch to control the power-on and antenna switching.

Not having another amateur to help I was not able to transmit from the control location and for me to monitor at the radio location (100Km apart)

Today I tried some SSB transmissions.  I am getting what has been described as a "pulsing heterodyne" on the signal. If I press the PTT, but do not say anything, I can see the power meter pulsing,  showing significant output.  It does not seem to be related to the output power, When I reduced the output from 80w down to 15w and I could still see the same thing happening.

Any suggestions as to what might be causing this, and how to cure it. 

The RRC,Webswitch and ancillary devices are on one  PSU, and the rig is fed from a separate 25A supply.

I have put several clip-on ferrite cores on the TTL cable and used the supplied cable for the aux/mic cable.

73,
Dave, G3UEG

dj0qn

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Re: New installation - TX problem - RX brilliant
« Reply #1 on: 2010-06-17, 16:51:44 »
Dave,

I had a very similar, if not exactly the same problem.

It turned out that one of the straps (MIC GND) was not all the way in the socket, which wasn't visible to the naked eye (at least my lousy naked eyes). It could be that it came loose in transit, or I just didn't push it in all the way. I ended-up replacing the strap, since it was bent a bit. They seem to fit best when the are in a straight arc. Either way, I would check there first.

73,
Mitch DJ0QN

G3UEG

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Re: New installation - TX problem - RX brilliant
« Reply #2 on: 2010-06-19, 18:37:54 »
I have made the 200km round trip to the remote site today to try and solve this pulsing problem on TX.  I have made some progress, but I do not understand the data I am getting.

I took the control end gear up to the remote site and operated all the equipment off the local LAN.  I still got the rythmic pulsing (pulse every 0.5 sec approx) of output when the ptt pressed but not speaking into the mic, with 10w output.  The antenna is an 80/40 trap dipole that is about 18m away from the shack, it is fed through a balun and I have a good shack earth system.  (All my other equipment works happily with this set-up at the 400w output level). I was planning on putting an SPE amp into the system...

The problem went away when using a dummy load.

I re-checked all the strappings and they looked and felt OK.

I switched off the tx monitor function.
I reduced the mic gain slightly
I have put 4 clip-on ferrites (two each end) on each of the cables between the RRC and the TS480 body.
I have powered the Radio RRC from an individual gel battery to decouple from everything else
I have put ferrites on the ethernet cable and the dc power cable

As a result of this I have got to the stage of being able to transmit at 50w,  above this level the pulsing  restarts but the frequency has reduced to 1 pulse every 3 secs approx.

I am surprised and disappointed that the RRC/Head unit is so susceptible to RF, for equipment that is intended to work in an RF environment.  I did just confirm that the rig and head connected as normal work perfectly well togther at the 100w level

Is this RF problem typical, or is there something else I should be doing, or is it possible there is a fault with the RRC?

Are other people operating successfully with antennas within 20m or less of the RRC?

73,
Dave, G3UEG



dj0qn

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Re: New installation - TX problem - RX brilliant
« Reply #3 on: 2010-06-19, 20:23:28 »
Sorry to hear that you are still having problems, even after making the long trip to the remote site.

Again, your description of the problem is virtually identical to the one I had, except that I didn't test it with a dummy load before I solved it. I neglected to mention that the problem with the strapping was at the remote unit and not on the RF side. I assume that you checked the strappings on both units, but wanted to mention that. You may wish to replace the MIC GND strapping, just in case. I couldn't see or measure the problem before I did.

My experience is that the RRC is very insensitive to RF. I did some quick RFI testing at the time by sending high power CW with the TS-480 through my SPE Expert into the SteppIR parked on the roof only about 4 meters above the RRC without a problem. I killed the DSL modem and had other strange things happen at that low height, but no effect on the RRC.

If the strappings wasn't the problem, then hopefully Mike or someone else can offer some advice. I hope that you can solve your problem, because this is really a great solution!

73,
Mitch DJ0QN




G3UEG

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Re: New installation - TX problem - RX brilliant
« Reply #4 on: 2010-06-19, 23:53:58 »
Thanks Mitch for your comments and encouragement..

Just to confirm I checked both the radio and control RRCs.. 

I don't know how I can actually **test** whether they are working as they should..

Mike, if you read this, can you let me have the spec of the wire for the strappings..  I am going to need to make some more, I have used 12 so far as once one has bent it is difficult to re-use it so I have just been using a new one..

73,
Dave, G3UEG

M0BPQ

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Re: New installation - TX problem - RX brilliant
« Reply #5 on: 2010-06-20, 13:19:47 »
I too am suffering from similar problems. I have a stack of ferrite on all cables, rebuilt my RRC to radio cables with shielded ethernet cable and can still only tx on some bands at the 50w level, others much less. Ther also seems to be a problem when I use my PC to generate CW during contests with character elements getting lost. The end of my inverted L is about 10m away from the radio.

Dave, I only live 20 minutes away from you. I'd be happy to help out if you think that an extra pair of eyes would be useful.
73
Steve
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G3UEG

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Re: New installation - TX problem - RX brilliant
« Reply #6 on: 2010-06-23, 14:25:22 »
Steve,

Thanks for your post.. I have sent an email direct to your address on QRZ.COM..  I wonder if you received it OK?  It would certainly be a help to work together on trying to sort this problem out.

73,
Dave, G3UEG

sm0mdg

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Re: New installation - TX problem - RX brilliant
« Reply #7 on: 2010-06-23, 23:10:07 »
I reduced the mic gain slightly

Try turn the "Codec inp gain" setting off on the radio side, this cured my RF feedback problems. It seems like the combination of RRC and TS-480 is very sensitive to RF feedback.

73 de Björn
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G3UEG

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Re: New installation - TX problem - RX brilliant
« Reply #8 on: 2010-06-24, 16:02:43 »
Hi Bjorn,

Thanks for the info...  but I am not quite sure I understand your comment.

The codec input preamp is only an option at the control RRC.

The codec parameters I have are as follows for the V4 hardware and the op-amp mod **not** done

CONTROL..  255 / 13 / OFF
RADIO..      255 / 0 

73,
Dave, G3UEG

W6SA

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Re: New installation - TX problem - RX brilliant
« Reply #9 on: 2010-07-31, 00:01:50 »
I hope you have resolved this problem by now but if not...

I had the same issue with audio noise being transmitted once I keyed the mike and I had not so much as even breathed into the mike.  Dummy Load was fine, don't ask me why.  Tried tons of ferrites. No difference.

Wrote to Mike and as an afterthought he suggested turning off the pre-amp.  Works fine now.  I seem to recall a similar issue with another piece of equipment in the past.

Now I see Mike has a modification to get around the noisy Op-Amp in version 4.  I have made a couple of contacts with excellent audio reports since turning off the Pre-Amp.

My current project is getting the unit to work wirelessly while parked outside a Starbuck's or any other hot spot.  It works in the shack and I believe it would have worked when testing yesterday if my pocket router had not gotten its switch in the wrong position.  I am using it in Client mode and unfortunately it does not supply a DHCP address to the Radio Control unit in that mode. 

I have to use IPCONFIG to see what the network is using for its settings and then pick an address that isn't being used.  I am going to stick with the higher end up around 250 and see what happens.

I do not have a remote station but purchased this system so I could continue with my hamming whenever I am away from home.  It will also come in handy to operate in the family room to see it the TVI is as bad as the wife says it is when I am on 10 or 12 meters.

I had no complaints until we got a cable/dvr box for the TV.  As far as know Cable TV uses the 10 & 12 meter frquencies.  No way to block that.

73,  Walt