ICOM IC-706 intermod problems on hi gain hf antenn

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eHam.net Forum : Elmers : ICOM IC-706 intermod problems on hi gain hf antenn

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ICOM IC-706 intermod problems on hi gain hf antenn	Reply
by W0ZD on July 17, 2002	Mail this to a friend!
I recently purchased a IC-706 MKIIG (SN#18416). I notice extremely strong broadcast intermod on twenty meters at different times of the day. It is there with or with out the pre-amp. (it is of course much worse with the pre-amp up to 40 db over S9 at times). I believe the signals are intermod because a (FT-1000 and IC 746) are clean as a whistle on the same antenna. I am using a Force 12 620/340 at 70 feet. I borrowed a friends IC 706 MKIIG and see the same problem. I have searched the internet and found no reference to this type problem. I purchased it primarily for mbile work but would like to use on occasions in the shack. Has anyone else noticed this ? jerryjtb@chilitech.net

RE: ICOM IC-706 intermod problems on hi gain hf an	Reply
by WB2WIK on July 17, 2002	Mail this to a friend!
I have not specifically noticed "broadcast intermod" with the 706 connected to a large antenna; however, I have noted -- many times -- the '706's inability to handle very strong signals, in general. When I plug one into my HF beam feedline at home, the '706 produces many signals that simply aren't there, and are nonexistent on my TR-7 or TS850S/AT. Images? Spurious responses? Intermod products? Difficult to qualify precisely, but it's "junk," and it's only there with the 706, and not with the "bigger" radios. So, my conclusion is the '706 is not equipped to handle extremely strong signals, and that's probably alright with about 99% of its owners. It gets rave reviews from the mobile/portable crowd, and I agree it's a wonderful little rig. WB2WIK/6

RE: ICOM IC-706 intermod problems on hi gain hf an	Reply
by K3WVU on July 17, 2002	Mail this to a friend!
I get the same thing at the lower portion of the 20M band and also between 15MHZ WWV and the beginning of the 19M International Broadcast band. It's very faint but it seems to be images of broadcast stations. I have a very large am bcb antenna about a mile from my house. I don't notice this stuff on my ICOM IC-718. I don't consider it a problem, though.

RE: ICOM IC-706 intermod problems on hi gain hf an	Reply
by K0BG on July 17, 2002	Mail this to a friend!
I've owned a 706 for about 2 years, and it's a couple of thousand numbers lower than yours. I operate mobile, and have never noticed the problem you speak of. Other users, however, tell me there is a problem with nearby AM stations. I live only 5 miles from a 10,000 watt AM station without any problems with my MarkIIG. There are some strong birdies, particularly on 6 meters, but that is it. The preamp is not all that good, but it doesn't seem to matter if it is on or off. What does matter, is the noise blanker. When the NB is on, ANY strong station on the band causes intermod and it can be exasperating. It sure is an incentive to spend time quieting the QRN from the various parts of ones vehicle. Alan, KØBG

RE: ICOM IC-706 intermod problems on hi gain hf an	Reply
by KL7IPV on July 18, 2002	Mail this to a friend!
I haven't noticed any of those things with my MKII but I do have lousy audio on FM if I forget to turn the NB and DSP off before going to an FM signal. I use both a vertical and a HyGain Explorer 14 triband beam. I think it is a great radio too. It is my second version. 73 Frank KL7IPV

RE: ICOM IC-706 intermod problems on hi gain hf an	Reply
by KC2HPH on July 18, 2002	Mail this to a friend!
I have noticed a similar problem, whether it's intermod or not I don't know. When I installed a Diamond X-510 I started to get iterference of some type on 2 meters. It happens when one of 2 nearby (10 miles) repeaters transmits while I'm listening to another frequency, it doesn't seem to matter how far away (in frequency) the signal is from the other repeaters. This only started when I got the new antenna and doesn't happen on a Yaesu FT-847, so I'm assuming it's a problem in the 706. Other than that, the 706 is a very good radio <-(opinion). Jon Rudolph KC2HPH

RE: ICOM IC-706 intermod problems on hi gain hf an	Reply
by K0BG on July 18, 2002	Mail this to a friend!
Just for funsville, I drove over to the transmitter site of our local 10KW AM station. The 706 didn't hickup until I turned on the Noise Blanker. WOW! Sounded like Channel 19! Best make sure it's off. Alan, KØBG

RE: ICOM IC-706 intermod problems on hi gain hf an	Reply
by K5DVW on July 18, 2002	Mail this to a friend!
I've not noticed the problem on HF, but on my base set up antenna, 2m is basically useless due to intermod. I have had to build a bandpass filter for 2m/440 that I keep in line. It's really sad that ham radios don't have decent front end performance, especially for mobiles or base units. HT's I can understand since it's mostly about current consumption and size.

RE: ICOM IC-706 intermod problems on hi gain hf an	Reply
by HB9PJT on July 18, 2002	Mail this to a friend!
At a friends installation I have seen the same problem. He has a 706mkII with a wire antenna and an SGC tuner. Over 14.2 Mhz there are th BC station again which are realy over 7.1 Mhz located (European BC-band). That is the 1st harmonic, generated from the RX of the IC-706 with oder without attenuator. The problem is not present with other equipment. Maybe a tuner with T-arrangement (one L and two C's) could help because of the highpass characteristic.

RE: ICOM IC-706 intermod problems on hi gain hf an	Reply
by WB2WIK on July 18, 2002	Mail this to a friend!
No question an antenna tuner often helps reduce overload, intermod and all sorts of "baddies" created by strong, out-of-band signals. One reason the IC-706 is not in my shack is its lack of an internal ATU. Unfortunately, a lot of ham gear having an internal ATU has it in line with the transmitter only, and not the receiver! (Which, obviously, is plain silly.) I changed my TS850S/AT to place its ATU in line on RX as well as TX and use it all the time, even when dealing with antennas providing a perfect match, because the ATU definitely helps the receiver by its bandpass function. Possibly, an external tuner on the IC-706 being plagued by BC QRM would help a great deal. WB2WIK/6

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