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Re: [TowerTalk] HP8761A

To: Kevin Normoyle <knormoyle@surfnetusa.com>
Subject: Re: [TowerTalk] HP8761A
From: jimlux <jimlux@earthlink.net>
Date: Tue, 26 May 2009 20:42:40 -0700
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Kevin Normoyle wrote:
> John W5NNH wrote 
>> Okay, then it looks like I'll be going with the Tohtsu CZX-3500.  I can 
>> mount that in a case reasonably easy and feed it with 12 vdc through the 
>> rotator cable.
> 
> 
> 
> at $110 for a single Tohtsu 3500, is that really a cost saving for this 
> kind of outdoor switching?
> 
> Just did a quick look, because my remembering of this is that most 
> people who try to do a cheaper homebrew come to appreciate the different 
> issues in making something that works well?
> 
> comparison:
> 
> ICE has (thru array solutions)
> http://www.iceradioproducts.com/rfswitch.html#3
> which claims:
> "standard rating 7,500 Watts PEP / ICS, insulation rating of poles and 
> relay armatures 2000VAC, switching time 11ms., usable up to 500 feet 
> from feed voltage source, 50 / 75 ohms, 0.1 db insertion loss, DC-30 MHz
> 
> ... each switching unit contains a resistive heating element which may 
> be switched on and off from the control source or left on 24 hours per 
> day (total cost about 5-7cents per year), keeping the relays and chassis 
> housing warm and dry -- even in harsh environments. All models rated for 
> indoor / outdoor service"
> 
> 2:1 for $58 or $62
>


Difference between 7500W PEP/ICS (whatever that really means.. what sort 
of peak/average ratio are they assuming, and what sort of duty factor 
for that "I"CS) vs 1000W PEP (presumably CW)

The Tohtsu is speced to 4GHz, and probably has a better match (although 
for HF, it's probably not all that important)

The ICE switch doesn't have a spec for isolation, the Tohtsu has at 
least 65 dB.

The Tohtsu is spec'd to operate from -25 to +50C, no spec on the ICE.

Basically, the difference between a "real" RF switch and a standard 
relay used for RF.
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