[amsat-bb] Coax routing question
Stephen E. Belter
seb at wintek.com
Fri Dec 19 03:07:07 UTC 2014
I have the same antennas mounted in the "X" orientation you describe. On the 2M antenna, I changed the mounting of the element with the coax connector so that it points towards the front of the antenna instead of the rear. That makes it easier to route the coax up the boom to the cross-arm.
Make sure you follow the mounting suggestions in Kent Britain's article mentioned by Gary, KK0CD, and center the cross-arm between the 2M elements.
In my case, I took the coax off the rear of the 70cM antenna as recommended by M2. I use a support similar to the one recommended by Norm to bring the coax back to the cross-boom. The spacing between the 70cM elements is really small, so it is much more difficult not to affect the pattern.
I would avoid the 90-degree elbows, as you'll suffer additional connector loss. Some of them contain a hairpin spring for the center conductor to make it less likely that the internal connection will flex and break. That's a great idea at HF, but acts like an RF choke at UHF, making the loss even worse! :-(
73, Steve N9IP
Steve Belter, seb at wintek.com
On Dec 17, 2014, at 5:34 PM, Dave J <ddjulian54 at yahoo.com> wrote:
> I am assembling a satellite antenna system using the M2 2MCP22 and 436CP30
> circularly polarized antennas with polarity switches and a fiberglass cross
> arm. The M2 instructions specify the feedline going off the rear of the
> antennas. Mechanically I would prefer to route the feedline and polarity
> control up the boom to the cross arm. I plan on mounting the antennas in a
> cross pattern with no element parallel to the cross arm. Since the RF
> connectors face the rear I was planning on making a hairpin loop at the rear
> of the boom or using good quality 90 degree elbows. Just wondering if folks
> have had experience setting things up this way and what effect (if any) this
> would have on performance.
> Thanks and Happy Holidays
> Dave WB9YIG
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