[Lowfer] RG-58 as TX loop conductor

Tue, 23 Sep 2003 14:53:33 -0400

Brian,

Thanks for the input on your experience with shielded cable in the Medfer 
band. Could be even a larger effect compared to Lowfer frequencies. Jay and 
I are working on the reasons for the big discrepancy in calculated vs 
measured values for my 50/50 loop using the RG-58. Could even effect my 
predicted loop performance numbers for the popular RG-8 Lowfer loops 
(Warning: JA).  It's interesting that the spec I have for my RG-58 cable 
indicates a .8 ohm DC resistance for the shield at a length of  200 feet. 
This seems very high, but will confirm tonight on the actual loop. If I add 
a little resistance for the shield at 185k, and some more for typical soil 
losses, I calculate exactly the measured 23% gain in current that I 
experienced last night!

Jay: I forgot that I can use my Rac meter to measure the AC resistance of 
the loop independent of the transmitter. Duh!

Bill A

>When I put up a test loop for the lower end of the medfer band, I started 
>with a single #14 conductor which was extremely poor.  The loop was about 5 
>feet off the ground.  I changed to loop to some cable that had braided 
>shielding around it about .5 inch in diameter and it only improved the 
>signal received at a remote location 6 miles a way by about a db or so.  
>After this I replaced this with .75 inch copper water pipe for significant 
>improvement that met the calculations on the loop program.  I don't have 
>all the details on the reactance or current input of the loop but I did 
>experience that the copper braid did not perform as expected vs. the single 
>#14 solid conductor.  The loop has since been scrapped for other projects.  
>Maybe if I get motivated I'll try it again as I did not compare it to 
>another known working antenna or take the fs measurements to say how 
>inefficient it was.
>
>Brian Helms
>
>>From: "Bill Ashlock" <[email protected]>
>>Reply-To: [email protected]
>>To: [email protected]
>>Subject: [Lowfer] RG-58 as TX loop conductor
>>Date: Mon, 22 Sep 2003 21:26:48 -0400
>>
>>Jay,
>>
>>>Will have my RG-58/#12 number for you later.
>>
>>Well, I beat you to it. The improvement for changing from #12 to  RG-58 
>>was not as good as predicted. Darned if I didn't forget to measure the 
>>'before' loop current in the rush to beat the rain and outlast the 
>>mosquitoes, but the input current increased only by 23%, against my 
>>prediction of 40%.  I'm either lossing my mathematical touch or a braid of 
>>cooper wire isn't nearly as as good as a copper pipe of the same diameter.
>>
>>What was your prediction based on the .25 ohm ground loss I gave you?
>>
>>Bill A
>>
>>_________________________________________________________________
>>Instant message with integrated webcam using MSN Messenger 6.0. Try it now 
>>FREE!  http://msnmessenger-download.com
>>
>>_______________________________________________
>>From the Lowfer mailing list
>>Send messages to: [email protected]
>>To sub/unsub visit: http://mailman.qth.net/mailman/listinfo/lowfer
>
>_________________________________________________________________
>Share your photos without swamping your Inbox.  Get Hotmail Extra Storage 
>today! http://join.msn.com/?PAGE=features/es
>
>_______________________________________________
>From the Lowfer mailing list
>Send messages to: [email protected]
>To sub/unsub visit: http://mailman.qth.net/mailman/listinfo/lowfer

_________________________________________________________________
Help protect your PC.  Get a FREE computer virus scan online from McAfee. 
http://clinic.mcafee.com/clinic/ibuy/campaign.asp?cid=3963