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Hi guys:

I acquired a 2 bay, 6 meter Sinclair antenna at our main
repeater site. It was tuned for 45 Mhz and that was verified
by checking the return loss. At my 6 meter repeater output,
the return loss is about -10 db (a little over 2:1 SWR).

Is it practical to use a tuner to bring it down to the 1.5:1
range or less? I'm worried that the tuner will be too sharp
to let the RX pass.

Any recommendations?


Tedd Doda CET CEO

Lazer Audio and Electronics

packet ve3tjd@va3sed
e-mail lazer@...

Tedd:

Gain is also a function of frequency. You can suffer the loss in a matching
network, but your antenna gain will be lower, too. I wouldn't recommend it
unless you have no other choice.

John NI0K

And if I might add... I would run a circulator and harmonic filter on
this one, especially if you run a solid state PA.

David


John wrote:

How high is the antenna? Is it feasible to get it down and trim it to the
correct
freq? How much feedline is between the ant and the tuner??? Your feedline is
going to increase its loss if the swr is high. That in and of itself may make
the antenna gain zero or lossy!

$.02

Ed N3SDO

Gain is also a function of frequency. You can suffer the loss in a matching
network, but your antenna gain will be lower, too. I wouldn't recommend it
unless you have no other choice.

John NI0K

----- Original Message ----- >

I acquired a 2 bay, 6 meter Sinclair antenna at our main
repeater site. It was tuned for 45 Mhz and that was verified
by checking the return loss. At my 6 meter repeater output,
the return loss is about -10 db (a little over 2:1 SWR).

Is it practical to use a tuner to bring it down to the 1.5:1
range or less? I'm worried that the tuner will be too sharp
to let the RX pass.

Any recommendations?

Ed Bathgate RMA Dept (724) 772-8785
pager (412) 649-6773

Tedd says:

The antenna is 400 feet up, on the side of a 600+ foot tower.
It's 1/2" Andrews Heliax, and from the antenna to the shack
I would say maybe about 475 feet? The shack is about 75
feet from the tower, plus the 400 feet to the antenna.

Well, that will make for an interesting experiment.
I would agree to use a tuner between the feedline and
the repeater. My suggestion would be to tune for lowest
tx swr. You probably will lose some on the rx, but bad
sensitivity is easier to live with than fried PA transistors!

73 & good luck!

Ed N3SDO


Ed Bathgate RMA Dept (724) 772-8785
pager (412) 649-6773

On Wed, 28 Apr 1999 06:44:01 -0500, John wrote:

Gain is also a function of frequency. You can suffer the loss in a matching
network, but your antenna gain will be lower, too. I wouldn't recommend it
unless you have no other choice.

Yes, I agree. But Gain is also a function of height, and this
thing is 400 feet higher than my Ringo, hi! I guess we'll find
out how the Mastr II likes SWR's of 2 to 1 this weekend, after
we reroute the Heliax to our shack.

I presume you meant that you would avoid the antenna?


Tedd Doda CET CEO

Lazer Audio and Electronics

packet ve3tjd@va3sed
e-mail lazer@...

On Wed, 28 Apr 1999 08:22:57 -0400, DPW wrote:

And if I might add... I would run a circulator and harmonic filter on
this one, especially if you run a solid state PA.

Do they make circulators for 6 meters?


Tedd Doda CET CEO

Lazer Audio and Electronics

packet ve3tjd@va3sed
e-mail lazer@...

On Wed, 28 Apr 1999 09:17:47 -0400, Ed Bathgate, RMA Repair Dept x8785 wrote:

How high is the antenna? Is it feasible to get it down and trim it to the
correct freq?

The antenna is 400 feet up, on the side of a 600+ foot tower.
We were contemplating getting a rigger up and at least put
a shorting bar on the dipoles, but the TV station is replacing
the Tower within the next 3 years and we (the club) can't
justify it at this time.

How much feedline is between the ant and the tuner???

It's 1/2" Andrews Heliax, and from the antenna to the shack
I would say maybe about 475 feet? The shack is about 75
feet from the tower, plus the 400 feet to the antenna.

Your feedline is
going to increase its loss if the swr is high. That in and of itself may make
the antenna gain zero or lossy!

Agreed. I guess we'll find out this weekend. It will
only cost us a few man hours to reroute the heliax.


Tedd Doda CET CEO

Lazer Audio and Electronics

packet ve3tjd@va3sed
e-mail lazer@...

Tedd Doda wrote:

From: "Tedd Doda" <lazer@...>

On Wed, 28 Apr 1999 12:15:06 -0400, Ed Bathgate, RMA Repair Dept x8785 wrote:

Well, that will make for an interesting experiment.
I would agree to use a tuner between the feedline and
the repeater. My suggestion would be to tune for lowest
tx swr. You probably will lose some on the rx, but bad
sensitivity is easier to live with than fried PA transistors!

My feeling exactly! We have a rigger coming to change our
VHF antenna and feedline at the same site (different tower),
so I may ask him how much he would charge just to install a
shorting strap on each dipole (can't make it much worse, hi).

Tedd Doda CET CEO

I wonder about the use of a shorting strap. We
use VHF loops (DB-224)from commercial stuff on 2
meters by adding a stub on the end of the loop.

So the total length is what counts. If you strap
the loop, it may go up in freq, but I bet not much.
Unfortunately, the loops are probably frozen and can
not be smacked shorter.

Good luck, I do not want to rain on the parade,
but it may be worth trying on the ground first,
this one knows how much to "strap short" or
shorten the elements 73 carl w7exh

On Wed, 28 Apr 1999 12:15:06 -0400, Ed Bathgate, RMA Repair Dept x8785 wrote:

Well, that will make for an interesting experiment.
I would agree to use a tuner between the feedline and
the repeater. My suggestion would be to tune for lowest
tx swr. You probably will lose some on the rx, but bad
sensitivity is easier to live with than fried PA transistors!

My feeling exactly! We have a rigger coming to change our
VHF antenna and feedline at the same site (different tower),
so I may ask him how much he would charge just to install a
shorting strap on each dipole (can't make it much worse, hi).


Tedd Doda CET CEO

Lazer Audio and Electronics

packet ve3tjd@va3sed
e-mail lazer@...