Topband: How Good is Good Enough?

[ZR]

I went with the 2 BOG's stricty because of noise crud from yuppie neighbors 
in line with the SE and SW elevated 2 wire reversibles. When they shut off 
their toys and go to bed the elevated ones are better.

The SW one stops 50' from their house which is too big for the property 
anyway.

If you need a preamp on any Beverage you have a problem IMO. Its too long, 
poorly terminated or there is a lot of feedline loss.

Im running 750' of 1/2" CATV hardline to the relay boxes and well decoupled 
quad shield RG-6 to the antennas. Most are short runs but one is about 200' 
that is lightly stapled to trees in parallel with but 15-20' away from the 
antenna which is the 750' E/W and one of the quietest since it points into 
deep woods both ways.

The very first step in evaluating a system is to directly terminate the 
feedline far end in a 50 or 75 Ohm resistor. I use the standard CATV screw 
on F connector 1/4 W type. There should be dead silence from the BCB on up; 
I test to 20M.

Getting rid of common mode is easy but expensive. It requires lots of 31 mix 
FT-240 toroids, ground rods and attention to connector assembly/sealing. 
Transformers should be BN73-202 binocular core only with particular care to 
match the real impedances and isolate primary from secondary for minimal 
capacitive coupling. Balun core windings and transformers wound on toroids 
have poor isolation.
The advertised premade boxes are a pure waste of money if you want the best 
results. You need to know your own ground resistance and not just buy 
something generic simply because someone who writes a web page says so.

I dont know if Id trust trying to use a resonant dipole on the ground to 
determine the VF of a non resonant wire. In any case keep the VF at about .6 
or higher when determining the maximum length of the BOG, Slinky, or any 
other Beverge form.

Carl
KM1H


----- Original Message ----- 
From: "Pete Smith N4ZR" <n4zr at contesting.com>
To: <topband at contesting.com>
Sent: Monday, March 12, 2012 7:29 AM
Subject: Re: Topband: How Good is Good Enough?


> This is exactly why I got to looking at BOGs - I lack the space in a
> Northeasterly direction (Northwest too, for that matter).  Mine is 220
> feet, as suggested by some experiments with the resonant frequency of a
> dipole laid on the ground to derive a velocity factor - a technique
> suggested by K2AV.
>
> My thinking on putting the preamp at the antenna end was that I would
> improve the SNR and potentially the directivity by amplifying the
> desired signal before sending it down the coax where common mode signal
> pickup, to some degree, seemed inevitable.  But if the preamp is
> amplifying those signals as well, then I clearly need to rethink.
>
> 73, Pete N4ZR
> The World Contest Station Database, updated daily at 
> www.conteststations.com
> The Reverse Beacon Network at http://reversebeacon.net, blog at 
> reversebeacon.blogspot.com,
> spots at telnet.reversebeacon.net, port 7000 and
> arcluster.reversebeacon.net, port 7000
>
>
> On 3/11/2012 9:52 PM, ZR wrote:
>> Very possible on your farm Mike, time to experiment I'd say.
>>
>> Carl
>> KM1H
>>
>>
>> ----- Original Message -----
>> From: "Mike Waters"<mikewate at gmail.com>
>> To: "topband"<topband at contesting.com>
>> Sent: Sunday, March 11, 2012 9:19 PM
>> Subject: Re: Topband: How Good is Good Enough?
>>
>>
>>> Thanks, Carl!
>>>
>>> Seems to me that laying on the ground, the VF would be considerably 
>>> lower,
>>> and so we could shorten them.
>>>
>>> 73, Mike
>>> www.w0btu.com
>>>
>>> On Sun, Mar 11, 2012 at 7:58 PM, ZR<zr at jeremy.mv.com>  wrote:
>>>
>>>> Ive said several times that my 500' BOG's dont need a preamp. The 
>>>> signal
>>>> level may be 5-6dB lower
>>>>
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