[FADCA] Separation of UHF beams at FPAC sites

[fadca@mailman.qth.net]

bud thompson wrote:
 
> Doug- I don't mean to put you on the spot - anyone can answer this...
> When we may only have 30 ft of tower space or less to use, what are
> we going to do with the other two antennas on a four UHF port switch?
> Even at that, on a roof-top site 30 ft of vertical separation may not
> be possible at all.  What are the practical aspects other than
> cut/try? 
> 
> PO and receiver front ends need to be addressed.  Where desense is
> observed, can the PO on one or more co-located transmitters be
> reduced to minimize the desense w/o degradation of the intended
> service?  My  limited experience with these Motorola Mitreks is that
> with 30-35w  and just 1 MHz of separation, and the 6-el beams at the
> same elevation on the tower (but back-to-back - one horizontal, one
> vertical), we've experienced little degradation by either port to the
> other. (However, after chatting with Doug at W. Palm last month, I
> now plan on running some more definitive tests!). At that, I believe
> our general experience with Mitreks indicates they offer the best
> bang for the buck so far as minimizing off-channel receiver desense.
> Commercial radios by other manufactures may do as well or better. 

Here in Tampa we have used low power radios and high gain antennas
to offset the problem. In fact the old link from Tampa to St.Leo had
a Motorola GM300 on the far end and a TECK radio on our end, but we
had some high gain yagi's on each end (St. Leo had a 10 or 15 element
yagi on that end, I think we had 8 elements here).


> 
> Can we make the following caution at this time for those
> contemplating more than one UHF backbone at a site?
> 
> "It is recommended that typical commercial 'mobile' UHF radios (i.e.
> Kenwood, Icom, Yaesu, Alinco, etc, etc,) not be used for this
> service." 

Indeed if you can use the low power devices in place of the high
power boxes, life in general is a lot easier, besides the low power
ones are usually cheaper than the high power ones. Also a lot of
them have better front ends than the synthesized radios particularly
the ham boxen. The commercial ones will have better front ends, unless
you get one of the "wide banded" ones that can be moved from dc - light
the tradeoff is that it is also open to all of the noise that can come
through the front door, this is one of the reasons that ham boxen
do not work well in a high noise environment, the front ends usually
crash in misery from all of the high power commercial stuff that is
near the radiio.


*****************************************************************
This e-mail and any files transmitted with it are confidential and are
intended solely for the use of the individual or entity to whom it is
addressed. If you have received this transmission in error, please notify
the sender immediately and destroy any hard copies you may have printed and
remove all copies of the e-mail from your hard drive. Opinions, conclusions
and other information in this message that do not relate to the official
business of Utility Partners, Inc shall be understood as neither given nor
endorsed by it.

Visit us on the web at http://www.utilpart.com 
*****************************************************************