[Premium-Rx] WJ8718 A-6 Front Pannel Interconnect HELP!

[David McGinnis]

David McGinnis
Senior Deputy Sheriff,
Missoula County Sheriff's Department.
Communications Systems Coordinator,
Missoula County Department of Emergency Services.

200 West Broadway
Missoula, Montana 59802
office:   (406)829-4277
cellular: (406)531-0303             
>>> "Ahmet Gundes" <ahmet-m at usa.com> 01/30/04 1:13 PM >>>
Hello Mark

It would be interesting to know model numbers and manufacturers
for these HF NVIS types so I can look into this.  This is a
very interesting subject for me.

Most of the models i've seen are for mobile applications such
as tanks and Humvees. Where their choice is low VHF to UHF.
I would like to build one that would cover lower bands which I
am working on. If you could please send specs and even pictures
of the Collins antenna it would be great to see details. Since
Collins no longer makes any HF equipment ( to the best of my
knowledge the only name left around is Collins filters and 
Rockwell Collings making aviation products ) it is hard to find
such items and their specs.  A good antenna system is a must to
complement these high performance receivers.

In the current market, there are very few manufacturers that
make HF antennas that I know of. Checking the types they make would
ne quite interesting and educating.  

B. regards
Ahmet

> Ahmet,
>  
> HF NVIS antennas do indeed exist and are plentiful, I have one at home
and believe it was made by Collins. I have also seen more elaborate
versions that are designed for higher power than mine that use a
suspended tuner at the feed point of the crossed inverted Vs. The HF
NVIS antennas are not the same configuration as you described the
VHF/UHF NVIS antennas as being but they are called out as being NVIS
antennas on the name plate, sorry but I don't have the model numbers
handy at the moment.
>  
> Mark


Subject: [Premium-Rx] Broad Bandwidth HF RX Antenna + NVIS Antenna
 
> 	RE: NVIS Antennas
> 	
> 	I would like to add one more thing to the NVIS subject
> 	and its use as high-incident antenna:
> 	
> 	Most NVIS antennas used by the military ( you can find some
> 	explanation on this issue on the web site of Shakespear
> 	company that makes NVIS antennas ) are for VHF and UHF.
> 	
> 	This is basically due to the size/construction contstraints.
> 	These antennas are used on military vehicles and size is
> 	limited naturally. In order to have NVIS / High Incident
> 	angle, the antenna is made quite cleaverly as a Center
> 	Fed Vertical Dipole ( most companies keep this as a little
> 	trade secret ).  These antennas have "near vertical" dipole
> 	performance. They can be used usually as low as 30MHz as they
> 	are made to cover the military VHF bands.  However if the
> 	vertical you have is not a Center-Fed Vertical and it is
> 	a military monopole type then they are not NVIS type antennas
> 	in its true sense.  The "old" Telex 4331 is a Center-Fed
> 	Vertical and I believe you can get these from surplus dealers.
> 	I have not seen any NVIS HF antennas that can go down to
> 	say 15MHZ range or so. They would have to be made for special
orders and they are not commercially available. 

One other way to experiement with the Angle Of Incidence is to
 	Tilt the Monopole ( usually about 10 - 20 Degrees ) as you will
	see some hardware on military vehicles to do this. It helps a
bit.
> 	
> 	Regards
> 	A. Gundes
> 	
> 	
> 	
> 	
> 	> Well it looks like this thread has finally died down, I would
like to thank you all for your input on my request for broad bandwidth
HF antennas ideas. In a previous job I visited quite a few National
Guard facilities and they were all using the B&W T2FD for HF
communications. This is what originally got me interested in this
antenna for band cruising. I really don't need an antenna that eaks out
the last bit of performance for HF receiving purposes due to the high
noise floor on the HF bands. I also saw a web site that did extensive
modeling of the T2FD and if anything this scared me away from the idea
of using it once I saw the analysis, however we all know that what a
computer predicts and real world results are often quite different, this
is why your input was so important to me. I also like the antenna idea
that Al mentioned and to take it one step further I and probably most of
you have seen the broadband dipole idea where a separate dipole is cut
for each frequenc
 y b
> 	 and and they are all attached to a common feed point. My
question is has anybody tried this out and how did you like, also has
anybody modeled it and what did the feed point impedance look like over
frequency? Finally thanks for bringing up the NVIS antenna, it reminded
me that I have one packed away somewhere, I think I'll set it up and see
how well it works, even if it is a high angle antenna it might work out
well for skywave.
> 	> 
> 	> Mark
> 	
> 

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