Dave:
Shouldn't the RX's AGC be turned off for these measurements, too?
73 de
Gene Smar AD3F
-------------- Original message ----------------------
From: "David Hachadorian" <k6ll@adelphia.net>
>
> ----- Original Message -----
> From: "W7CE" <w7ce@curtiss.net>
> To: "W4ZW" <w4zw@comcast.net>; <towertalk@contesting.com>
> Sent: Saturday, August 19, 2006 7:15 AM
> Subject: Re: [TowerTalk] small antennas
>
> > Having a 402CD 14' above the SteppIR (less than 0.3
> > wavelength) will most likely reduce the F/R performance of
> > your SteppIR.
>
> The 40-2CD normally stacks well with a tribander, but may
> affect 18 and 24 Mhz. It can also affect 10, 15 or 20 if an
> "unlucky" length of feedline is dangling off the 40-2CD's
> driven element.
>
> The easiest way to check for interaction between two
> antennas is to do a quick front-to-back experiment with a
> local ham, who is located 200 meters to several miles away,
> with line of sight. If two antennas are interacting, front
> to back ratio is the parameter that is degraded most, and is
> therefore the most sensitive indicator of degradation.
>
> To do the experiment:
> 1. Point your antenna away from the local ham.
> 2. Have him transmit a brief key-down signal.
> 3. Note the s-meter reading.
> 4. Point the antenna toward the local ham.
> 5. Have him transmit another signal.
> 5. While he is transmitting, crank in fixed attenuators
> until the s-meter reading returns to the level noted in step
> 3.
> 6. Read the front to back ratio from the attenuator setting.
>
> Precision attenuators are nice, but the fixed
> attenuators/IPO/AIP on most rigs are fairly accurate, and
> should give you a good idea whether the front to back ratio
> is reasonably good.
>
> Sometimes just changing the 40-2CD's feedline, or
> shorting/opening its feedline when the antenna is not being
> used will solve interaction problems.
>
> Dave Hachadorian, K6LL
> Yuma, AZ
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