[TowerTalk] What am I missing....balun

[Jim Thomson]

Date: Fri, 17 Feb 2017 07:41:09 -0700
From: Chris <EZRhino at fastmovers.biz>
To: "towertalk at contesting.com reflector" <TOWERTALK at contesting.com>
Subject: Re: [TowerTalk] What am I missing....balun

Is there any chance this is an April Fool's joke?

Chris


On Feb 17, 2017, at 6:40 AM, ve4xt at mymts.net wrote:

> I've been trying to divine a defence for this box, but can't.
> 
> If I read K9YC's choke cookbook correctly, there's no way this could achieve the level of broadband choking claimed. Moreover, not only is there no need to enclose such a device in so expensive an enclosure, it would compromise power handling. And if you did, how do you mount it at the only place it does any good?
> 
> When it appears the best-performing choke in Jim's cookbook is nothing more than a frequency-specific number of turns of coax through, at most, $50 in ferrite cores, with no bulky enclosure, I just can't see why anyone would pay $900 for this.
> 
> Also, if the photo is akin to an "exemplar" piece of furniture, and the box is built to custom specifications, then the quoted specifications are meaningless anyway.
> 
> BTW, isn't the attenuation noted (called return loss) the only way any choke actually chokes?
> 
> I think Array Solutions has some 'splainin to do!
> 
> Then again, PT Barnum has never been proved wrong.
> 
> 73, kelly, ve4xt 
> 

####  jay at array solutions posted a note on the AMP  reflector on tower talk.   The unit is optimized for the 11m folks like I thought.   Hence the  26.980 mhz marker on the screen.  Kelly,  return loss is just another way of expressing SWR .
The higher the return loss, the lower the swr.  You sweep the unit and note the return loss.  IE:  what is the swr with the unit terminated with a 50 ohm  dummy load.   You would expect it to be dead flat or close to it, on the freqs of interest.
Same deal  with LP and  HP filters, or say an amplifier on bypass mode.   At the telco I worked at, we used return loss measurements  exclusively, and nothing was expressed in swr ratios. 

###  That is  RG-393 coax..  Double silver plated braids and  silver plated stranded center conductor.  Teflon dielectric and  FEP-9  outer jacket.  That stuff runs aprx  $7.00  per foot these days.   For  20-6m, type 43 is typ used .   If you look at the K9YC cookbook, he states either  31 or 43  used on 20-6m.   The price tag of the unit was not what I was on about, but the stated  1.8 to 60 mhz freq range on their site. 

##  The fancy test gear is what measures the actual choke Z and RS of the choke.  Knowing that, then you can calculate the attenuation in db of   any shield current.    I think  you are confusing shield current attenuation in db...with return loss attenuation, which is also in db. 

Jim   VE7RF