[TowerTalk] small antennas

[ersmar at comcast.net]

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 at adelphia.net>
> 
> ----- Original Message ----- 
> From: "W7CE" <w7ce at curtiss.net>
> To: "W4ZW" <w4zw at comcast.net>; <towertalk at 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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