Thanks Dave.

That was an excellent post. It's interesting that I've read testimonials
on eHam and other web pages that claim 15 to 20 years of service with the
G7-144 with no complaints. Then there are some that have had some issues.

The G6-144 is a bit more attractive to me right now due to the lower
price and being about 2/3 of the length of the G7. Interestingly, the G6
literature (available at http://www.dxengineering.com) says, "FCC
accepted for Repeater application at 6db gain based on EIA Standard
RS-239: gain compared to 1/2 wave dipole." I've never heard of antennas
being "FCC accepted for Repeater application" before. So now I'm curious
whether the G6 may be more rugged than the G7. At the very least there
won't be so much aluminum swinging in the breeze.

I am looking for antenna for our repeater. We tried pressing a
commercial antenna tuned for 155 MHz into service, but it just hasn't
worked out as we have severe desense. Its mounting is also far from
optimal. The calculated SWR at the antenna is approximately 1.8:1.

We were checking things over today and everything looks good when the
duplexer is terminated into a 50 ohm load, but varying levels of noise
exist at the RX frequency when the antenna is connected. It is
definitely our system as the spectrum is clear when the repeater TX is
off. It was too windy today to climb to the top of the grain elevator
leg the antenna is on to check at the end of the hardline with a
wattmeter and dummy load.

I like the idea of the G6 as it appears easy to handle and easy to
mount. We are limited by the framework of the structure and we have to
avoid having anything that would get in the way of the employees or
jeopardize their safety. Also, it needs to be safe for us to work with
as well.

The G6 appears to be two 5/8 wave radiators fed with Hustler's fiberglass
encased coil assembly. I have seen that the antenna is about 10 feet
tall, weighs about 7 pounds, and has a surface area of 1.4 sq ft. We can
mount a mast easily on the structure that will support a lightweight gain
antenna like the G6. A DB-224 would be nice, but it requires
considerably more in the way of mounting and manpower resources to do it
correctly.

Any suggestions are appreciated.

73, de Nate

--

"The optimist proclaims that we live in the best of all possible worlds,
the pessimist fears this is true."

In article ,
Nate Bargmann wrote:

Thanks Dave.

That was an excellent post. It's interesting that I've read testimonials
on eHam and other web pages that claim 15 to 20 years of service with the
G7-144 with no complaints. Then there are some that have had some issues.

The luck of the draw, I suppose?

The G6-144 is a bit more attractive to me right now due to the lower
price and being about 2/3 of the length of the G7. Interestingly, the G6
literature (available at http://www.dxengineering.com) says, "FCC
accepted for Repeater application at 6db gain based on EIA Standard
RS-239: gain compared to 1/2 wave dipole." I've never heard of antennas
being "FCC accepted for Repeater application" before.

I imagine that there may be some such regulations for some of the
commercial or public-safety bands? Minimum or maximum gains allowed,
or cleanliness-of-pattern perhaps?

I am looking for antenna for our repeater. We tried pressing a
commercial antenna tuned for 155 MHz into service, but it just hasn't
worked out as we have severe desense. Its mounting is also far from
optimal. The calculated SWR at the antenna is approximately 1.8:1.

We were checking things over today and everything looks good when the
duplexer is terminated into a 50 ohm load, but varying levels of noise
exist at the RX frequency when the antenna is connected. It is
definitely our system as the spectrum is clear when the repeater TX is
off. It was too windy today to climb to the top of the grain elevator
leg the antenna is on to check at the end of the hardline with a
wattmeter and dummy load.

It sure sounds as if you've got a less-than-good connection somewhere.

We had similar problems after a while with one of our "American
Legion" J-pole antennas, which use an all-aluminum construction. The
radiator and matching-arm rods were originally mounted with
set-screws, but on this particular antenna the connection had been
reinforced with a spot-weld. Due to flexure of the rods in the
breeze, the weld eventually became brittle and cracked... and the
antenna immediately exhibited severe desense due to broadband-noise
generation in the cracked junction.

Any suggestions are appreciated.

We're looking at some of Telewave's antennas, which I believe are
similar to the DB-224 in their basic design approach.

I'd also suggest that you take a look at the copper-pipe EDZ design at
http://www.tcarc.ca/public/2mdez.php, which would have gain quite
similar to the G6-144, I think.

The folks who run this page seem to like this antenna for repeater
service. Since it's a grounded, fully-soldered design (you can solder
the balun-attachment points to the matching stub) it ought to be quite
free of desense-causing corrosion/micro-arcing points.

I built one of these for our repeater system, scaled down for use as a
remote-linking antenna for the 440 band. Seems to have worked out
well so far. The only thing I'd do differently the next time I build
one, is wait to figure out the actual shorting-stub and balun
attachment points until the antenna is actually in place on the tower.
I tuned it in a free-space situation, and the presence of the tower
de-tuned it a bit (enough to notice on a meter, not enough to matter
in practice).

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

On Tue, 18 Sep 2007 19:02:11 -0700, (Dave Platt)
wrote:

In article ,
Nate Bargmann wrote:

Thanks Dave.

That was an excellent post. It's interesting that I've read testimonials
on eHam and other web pages that claim 15 to 20 years of service with the
G7-144 with no complaints. Then there are some that have had some issues.

The luck of the draw, I suppose?

The G6-144 is a bit more attractive to me right now due to the lower
price and being about 2/3 of the length of the G7. Interestingly, the G6
literature (available at http://www.dxengineering.com) says, "FCC
accepted for Repeater application at 6db gain based on EIA Standard
RS-239: gain compared to 1/2 wave dipole." I've never heard of antennas
being "FCC accepted for Repeater application" before.

I imagine that there may be some such regulations for some of the
commercial or public-safety bands? Minimum or maximum gains allowed,
or cleanliness-of-pattern perhaps?


There are none I know of. However, commercial systems are licensed by
ERP, so I would suspect that the antenna gain figures must be accurate
in order to get the ERP calculations correct.


Regards,

Bruce

On Thu, 20 Sep 2007 12:40:10 +0000, BB wrote:

There are none I know of. However, commercial systems are licensed by
ERP, so I would suspect that the antenna gain figures must be accurate
in order to get the ERP calculations correct.

Perhaps that is what they really mean, that the gain is certified for ERP
calculations.

73, de Nate

--

"The optimist proclaims that we live in the best of all possible worlds,
the pessimist fears this is true."