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Author Topic: Ten Tec Orion 1 with Broadcast Station Interference on Transmit  (Read 1444 times)
K4RVN
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Posts: 758




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« on: January 18, 2013, 07:14:33 PM »

I am about 6 blocks from an AM radio station. The Orion I just bought will put out full power in the SSB mode in daytime due to the transceiver picking up the station when push to talk for transmit is
used. The receivers are not affected by the station in receive. When I use ptt on the mic, I hear the station through my headphones or the radio speaker. Let it go, and normal receive. The ALC light indicates activation and the watt meter shows full set power out and even keys the amp so I cannot use the Orion. At night when the station power is reduced the transceiver operates as it should.
I have an Ice broadcast filter that blocks the station interference for my Omni 6 plus beside the Orion. It has no problems. The 7200 Icom had no problems when I installed a filter on it. I have tried both filters on the Orion with no improvement. The Orion now sits in a spot that the 7200 was in using the same hook up. I did try running a 1 inch wide braided ground to the Orion, no change noted.
Any comments would be appreciated. As it stands now I use the Omni in daytime and the Orion at night.

Frank
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WB2WIK
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Posts: 20545




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« Reply #1 on: January 18, 2013, 07:20:13 PM »

I remember the film, The Graduate with Dustin Hoffman graduating from college and his elders giving him advice: One advice was "just one word...Plastics."

For what you describe, just one word: "Ferrites." Wink

I have an Orion and live very close to a 1.25 Million watt SW broadcast station.  If you think a 50kW AM BC station is something, try living down the road from one running over 20x that power.

I wrap all cords and cables through ferrite toroid cores.  Mike line, keyer line, all lines.  Bingo.  It all goes away. Smiley
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K4RVN
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Posts: 758




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« Reply #2 on: January 18, 2013, 07:32:53 PM »

Thanks Steve,
This is my lucky day having an elmer like you owning an Orion. It was so strange to me that the receiver had no interference until I tried to transmit with the push to talk.
I'll look for some ferrites. Any tips on a good place to buy those?

Frank
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WB6BYU
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Posts: 13027




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« Reply #3 on: January 18, 2013, 09:04:18 PM »

Sounds like the AM signal is being picked up on the mic cable.  Even a bypass capacitor
on the audio line might help.  But ferrite is good, too.

You can slip one or more ferrite beads on each wire, or wrap them all together through
a single core.  It might take a higher permeability core than for other HF uses since you
are trying to filter around 1 MHz.  Many of the cores that you find used a filtering on
computer cables appear to be optimized more for VHF, since that is where the radiation
will be worst from a reasonably short cable.

Lacking that you can try inserting an RF choke in the audio lead, and possibly the PTT
if needed.
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K4RVN
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Posts: 758




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« Reply #4 on: January 19, 2013, 07:10:44 AM »

Thanks for the replies. I have tried two different mics but using a heil hand switch for ptt. I don't know which ferrites to buy for toroids or beads right now. I have been looking on the net to find info
on them. If someone knows what I need I would appreciate the info, otherwise I'll keep reading for a time. I know where to buy them, just don't know which ones to buy. I'll probably call monday and ask the sellers.

Frank
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AC5UP
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Posts: 3825




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« Reply #5 on: January 19, 2013, 07:53:55 AM »

I think the hunch is that you're inducing enough power from the AM BCB station to fake out out the transmitter SWR foldback protection circuit. Remember that with a poor SWR a portion of the TX power is reflected back down the feedline and the SWR meter doesn't care if that voltage is on 1340 kHz or the DX Window of 20. The big clue for me is that this only happens when the AM station is at full power.

I'm going to guess that you're using a large-ish dipole cut for one of the lower bands as a triband beam is mostly deaf on the ol' AM BCB. Ferrites on the coax can help if it's a common mode issue (antenna + feedline = longwire) but if it's a case of an all-band Doublet that really likes talk radio the cure will be a smaller antenna, a high pass filter, or a tuned stub on the feedline.
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K4RVN
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Posts: 758




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« Reply #6 on: January 19, 2013, 04:43:51 PM »

Actually I am using a 5 band hex beam with a 1.03 to 1 swr as shown on the Orion. I have no tuner. The problem appears on all 5 bands with swrs all less than 1.5 to 1. Also same problem on Two 40 meter half square antennas which have very low swrs. It puts out full power as set which is 80 watts to my amp or 100 watts barefooted. Field strength meter hanging on the wall indicates no stray RF in the room on transmit or receive. The problem is as I see it that the broadcast station is modulating the talk circuit. The receivers are not affected, except when transmitting in the SSB mode. I can go down at night when the broadcast station is operating at reduced power or off the air and the Orion operates like it should. My Ten Tec Omni 6 plus always operates like it should, same mike and adapter by Heil. The Orion is detecting the radio broadcast while the Omni is not. Both are on the same ground system. Thanks for your input, I'll get a solution one of these days by trial and error if the books don't come through for me. I also have brocast blocking filters by ICE on each transceiver at the antenna connection. They have always worked on other radios in the past.
I can still operate as I have one transceiver that has no problem.

Frank
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WB2WIK
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Posts: 20545




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« Reply #7 on: January 19, 2013, 05:45:08 PM »

Radio Shack has "clamp on" ferrite filters sold in 2-packs for $7.95 last I checked (at least, here they do).

It might take 2-3-4 of these clamped on to work on HF.  Only problem is determining where to clamp them: Could be the mike cable, or other cables. 

I'd buy a few packs and experiment, but the problem should go away when you find the right solution.

With all such ferrite solutions, if you can wrap two or three turns of the cable through the filter, that can improve effectiveness by x4 to x9.
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K4RVN
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Posts: 758




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« Reply #8 on: January 19, 2013, 06:16:20 PM »

Thanks Steve, I'll try that. After I get the clamp ons, I'll post the results.

Frank
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K4RVN
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Posts: 758




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« Reply #9 on: January 24, 2013, 01:16:39 PM »

I found the solution to my Orion broadcast band interference. I'll post it here to pass on what I learned. First if you use ferrite beads the correct mixes for brocast frequency attenuation are
J or 75 material. You may be wasting your time with others. The ones I ordered have not arrived so here is what I found after some feedback with another ham K4TLJ. Reading the Orion manual
revealed a peculiar ground system for the mic circuit. The push to talk is grounded through the ring of the mic connection. The minus lead of the mic element is grounded through the chassis
ground. According to Ten Tec, these two grounds should not be tied together like many mics do. I checked my Ten Tec Heil adapter for my Proset and it was tied together. Ten Tec writes that this may increase Rf interference. I cut the push to talk wire and re routed it to the Heil adapter clamp screws on the mike adaptor where the wire passes through the adapter case. Now the two grounds are apart like the manual shows. There is no interference now in daytime, not even a flicker using the transceiver with my amp. My broadcast problems are solved and I can use my Orion.
Thanks for the replies.

Frank
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AD5ZC
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Posts: 69




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« Reply #10 on: January 24, 2013, 05:03:32 PM »

Nice catch and thanks for reporting back.
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KE3WD
Member

Posts: 5694




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« Reply #11 on: January 24, 2013, 06:02:30 PM »

Well, well, it was just Ye Olde Audio Grounde Loope...
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