[Boatanchors] Should dummy load oil ever need to be changed?

[Ray]

Yes, the length will have to be factored such that at your lowest 
frequency you have calculated (hopefully proves accurate) about 15 db of 
forward loss.  I have used cables with only 10db of loss in a pinch but 
that is not the best practice.

You can find the specified loss at various frequencies in the 
manufacturer's spec sheets.  Most Mil spec cables have similiar losses 
from most manufacturers.  There are some import cables which are 
questionable.

Ray, W4BYG

On 8/25/2012 2:04 PM, W2HX wrote:
> Does the length need to be something specific based on the frequency you're' using?
>
>   
> 73 Eugene W2HX
>   
>
> -----Original Message-----
> From: boatanchors-bounces at mailman.qth.net [mailto:boatanchors-bounces at mailman.qth.net] On Behalf Of Ray
> Sent: Saturday, August 25, 2012 1:14 PM
> To: boatanchors at mailman.qth.net
> Subject: Re: [Boatanchors] Should dummy load oil ever need to be changed?
>
> A useful dummy note note which may interest some:
>
> A piece of coaxial cable open or shorted at the far end with a loss rating of about 15 db or more at your frequency of interest, will provide a very nice dummy load.  It will provide a return loss of about
> 30 db (-15db forward loss and -15db reverse loss) .
>
> If you use a piece of cable rated at about 20 db of loss at your frequency of interest, you will have a near laboratory quality dummy load (40db RL).
>
> Make sure the cable is rated sufficiently for the power level you are going to use it with.
> Ray, W4BYG
>
>
> On 8/25/2012 12:09 PM, Bill Cromwell wrote:
>> On Sat, 2012-08-25 at 11:45 -0400, Wayne D Anderson wrote:
>>> Gentlemen
>>>
>>> It seems to me that in a hobby that found the use of a lightbulb as an acceptable  load, the Cantenna looks like a pretty good alternative.
>>>
>>> 73
>>> K7WDA
>> Hi,
>>
>> There are some radios that went to war with a light bulb for tuneup.
>>
>> 73,
>>
>> Bill  KU8H
>>
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