[Ant2] feed isolation while transmitting on HF [Ant1] when Mobil Posted by: "Charles Scott" cscott@gaslightmedia.com n8dnx Date: Mon Jul 3, 2006 12:21 pm (PDT) Sylvain: I believe my installation is about as good of a test of this as any. On one side of the back hatch in my Durango I have an SGC whip tuned by an AH-4 and on the other side is a 2 Meter collinear. This is very similar to the installation I had in my previous vehicle where I easily measured the HF energy coupled into the collinear with a watt meter (not lots, but measurable). In that vehicle I had an FT-100 which had a particular problem with that coming back into the VHF/UHF port and causing problems. This has not been a problem with the IC-7000. If you have any concern, I suggest you put a high-pass filter on the line from the 2M antenna. You can also use a HF/VHF band splitter (diplexer) installed with the common port toward the antenna and a small dummy load on the HF port. In looking at the service manual, it appears that there's an error in the block diagram. It shows a low-pass filter (LPF) from the common antenna line to the UHF TX/RX switch and a high-pass filter (HPF) from the common antenna line to the VHF TX/RX switch. When you look at the detail schematic, it's obviously the other way, as it should be. In any case, there's only low-pass filters between the antenna port and the VHF TX/RX switching diodes. I can't say how much power coming in from the VHF port it would take to cause a problem with that or other component damage, but if there was enough, it could be a problem. The other design concern would be RF coupling between that input and other components and wires inside the unit and that stray RF causing a problem (which was the problem with the FT-100 design). Since I haven't seen any problems with mine, I suspect there's no such issue in the 7000. Just for grins, I'll get my dummy load and watt meter out tonight and measure the amount of power I'm actually getting back in from the 2M collinear when transmitting on various HF bands. If nothing else, it should be educational. Chuck - N8DNX On Mon, 3 Jul 2006, Sylvain Faust wrote: > Hi to all... > > Just wondering before I start using the IC-7000 on HF in the truck the > implication of transmitting 100W on HF mobile while the antenna > (tarheel) on the hitch is 2 ou 3 feet away from the 2M 5/8 roof antenna > connected to the [Ant2] connector. Is the so-239 center switched to > ground while using the other antenna input? No diagram in the manual. > Same goes when using 2M or 440MHz instead of HF. > > Thanks in advance! > > 73, Sylvain VE2FET ========================================================================= [Ant2] feed isolation while transmitting on HF [Ant1] when Mobil Posted by: "Rob Sherwood" rob@nc0b.com nc0b Date: Tue Jul 4, 2006 8:42 am (PDT) How were the fireworks? I never considered this potential problem. I have a 2 meter 1/4 wave on the roof of my 4Runner, and then the ball mount for the whip / AH4 only a few feet apart. Never had any thing blow up. ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= ========================================================================= =========================================================================