There are quite a few Ten-Tec's in my shack and all of them suffer from
BCI overload to one extent or another. Truth is I have two AM
broadcasters within 1 mile of my location. This is what I have noticed:
1. My HyGain AV-640 vertical produces significantly greater BCI overload
than does my MA5B or my B&W folded dipole.
2. From worst to best: RX-350, Jupiter, Century 21, Scout, Paragon,
Omni-C, Omni-VI+
3. My TS-940SAT is fairly immune to the BCI overload (internal tuner in
or bypassed)..
4. Using an antenna tuner that acts as a high-pass filter eliminates the
BCI overload (MFJ-986 Differential-T)
5. Using L-style tuners are far less effective in eliminating BCI
overload (AT-11MP, Ten-Tec 229A)
6. Installing an I.C.E. model 406 BCB receive/transmit high-pass filter
(3.5-30 MHz) immediately after the transceivers takes care of all my
BCI issues. This filter allows you to transmit through it (100 watts or
so). I.C.E. has a filter that passes 160 meters too but I don't recall
that model number.
So my answer was to add the high-pass filter.
73,
Jerry, KG6TT
wq7x@cox.net wrote:
Bob:
Thank you for your advise and help.
There are two separate issues:
1. DSP overload
2. BCI Overload
BCI overload is from very strong AM station close to my house. I have just
measured with the scope and the max. P-P voltage =2.00V at 50 Ohms.
I didn't have much time (lunch time) to take this measurement. I need to make
sure that there is no error.
When I engage attenuator in my Orion (preamp OFF) the IMD signal drops proportionally.
That tells me that overload is happening before the attenuator. When I put external attenuator at the antenna input than IMD is gone.
Also, if I put external High Pass filter IMD is gone.
That is why I'm looking at diode protection circuit right before the
attenuator. Unless there is some other circuit before that and I didn't
find it yet.
There is no BCI IMD in K2 or TS930s or FT1000D.
Very strange.
Thanks,
Mark WQ7X
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