Hi.

I have a Barker & Williamson AP-10A apartment portable antenna,
which I am currently using with my Icom IC-725 100-watt all-band
transceiver. How do I set the counterpoise length for minimum SWR when
I cannot use the SWR bridge in my antenna coupler (MFJ-949B)? I ask
this because one of MFJ's technicians, in response to an email I sent
the company about six months ago regarding this issue, told me in no
uncertain terms that antenna couplers may not be used with the AP-10A
(any mismatches are to be corrected by setting the length of the
counterpoise, with the antenna connected directly to the radio). This
is all well and good, but how do I know when the SWR is 1:1 if I
cannot use the bridge in my coupler (by setting the antenna switch to
COAX 1 DIRECT or COAX 2 DIRECT)? I suppose I could watch the power
meter on the rig and experiment with the counterpoise length until I
had maximum output, but I don't want to do that as it may cause
unnecessary QRM. What should be my next step--to get an external SWR
bridge (which has no connection whatsoever to the antenna coupler), or
will tuning the counterpoise for maximum output be enough?

Thanks and 73,

Jeff Strieble, WB8NHV (mailto: )
Fairport Harbor, Ohio USA

On 10 Apr 2004 02:12:43 -0700, (Jeff Strieble)
wrote:
[snip]
how do I know when the SWR is 1:1 if I
cannot use the bridge in my coupler (by setting the antenna switch to
COAX 1 DIRECT or COAX 2 DIRECT)?
[snip]

Yes, the direct connection just bypasses the tuning components. Your
SWR meter is still functioning.

Danny, K6MHE

On 10 Apr 2004 02:12:43 -0700, (Jeff Strieble)
wrote:

Hi.

I have a Barker & Williamson AP-10A apartment portable antenna,
which I am currently using with my Icom IC-725 100-watt all-band
transceiver. How do I set the counterpoise length for minimum SWR when
I cannot use the SWR bridge in my antenna coupler (MFJ-949B)? I ask
this because one of MFJ's technicians, in response to an email I sent
the company about six months ago regarding this issue, told me in no
uncertain terms that antenna couplers may not be used with the AP-10A
(any mismatches are to be corrected by setting the length of the
counterpoise, with the antenna connected directly to the radio). This
is all well and good, but how do I know when the SWR is 1:1 if I
cannot use the bridge in my coupler (by setting the antenna switch to
COAX 1 DIRECT or COAX 2 DIRECT)?

I used the ap-10 back in the 80s with my Icom 735. I seem to recall
using my Bird wattmeter to measure the forward & reverse wattage as I
adjusted the counterpoise length. I see no reason why you can't use
the Coax 1 or 2 Direct connection on your tuner. When you do, you're
bypassing the tuner's capacitors and inductor, and just measuring the
feedline swr. Tune for maximum forward watts, minimum reverse watts. I
used to get the reverse watts down to nothing, even on 40 meters.

I had the counterpoise wire on an empty wire spool, and simply spooled
or unspooled the wire across the floor to adjust swr. I tuned at
minimum power, and then increased it to maximum. If you do your tuning
at minimum power, it shouldn't hurt your rig. And after awhile, you
can mark the wire length for each particular band.

Watch out for a lot of rf on the counterpoise. And don't be surprised
if your station is a little hot, rf-wise, as the counterpoise is
transmitting indoors. Still, the little whip in the window does a
surprisingly good job.

Bob
k5qwg


I suppose I could watch the power
meter on the rig and experiment with the counterpoise length until I
had maximum output, but I don't want to do that as it may cause
unnecessary QRM. What should be my next step--to get an external SWR
bridge (which has no connection whatsoever to the antenna coupler), or
will tuning the counterpoise for maximum output be enough?

Thanks and 73,

Jeff Strieble, WB8NHV (mailto: )
Fairport Harbor, Ohio USA

Jeff Strieble wrote:

Hi.

I have a Barker & Williamson AP-10A apartment portable antenna,
which I am currently using with my Icom IC-725 100-watt all-band
transceiver. How do I set the counterpoise length for minimum SWR when
I cannot use the SWR bridge in my antenna coupler (MFJ-949B)? I ask
this because one of MFJ's technicians, in response to an email I sent
the company about six months ago regarding this issue, told me in no
uncertain terms that antenna couplers may not be used with the AP-10A
(any mismatches are to be corrected by setting the length of the
counterpoise, with the antenna connected directly to the radio). This
is all well and good, but how do I know when the SWR is 1:1 if I
cannot use the bridge in my coupler (by setting the antenna switch to
COAX 1 DIRECT or COAX 2 DIRECT)? I suppose I could watch the power
meter on the rig and experiment with the counterpoise length until I
had maximum output, but I don't want to do that as it may cause
unnecessary QRM. What should be my next step--to get an external SWR
bridge (which has no connection whatsoever to the antenna coupler), or
will tuning the counterpoise for maximum output be enough?

If this is a real problem, it can be solved with an antenna analyzer
like the MFJ-259B, one of the handiest devices I have ever owned.
Got any friends with one?

You can also reduce the power out of your IC-725 to the absolute
minimum value, ID yourself, and experiment until you get it right.
At minimum power output, I doubt that any damage would be done.
--
73, Cecil, W5DXP



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