Coax Switching

Paul Blumhardt k5rt at VERIZON.NET
Sun Jan 7 09:00:57 EST 2007


Hi Bernie

	Several years ago, many of us contest types used "cascaded" Daiwa 2
position switches along with two B&W 6 position rotary switches to switch
various antennas to either of two rigs. It was rather complex to say the
least!. But it did work at 1.5KW power levels. Since then, a better solution
was developed (see the last ppg of this post)

	If we assume that the A/B switch (radio selector) has 40 db of isolation (a
reasonable figure for the typical Daiwa 2 position switch), and you are only
running 100 watts, the risk of damaging the "off-line" radio should be low.

	In your case, if you are using the Heathkit rotary coax switch to do the
A/B radio selection, I'm pretty sure that switch doesn't have more than 30
db of isolation between ports and its a good bet that you had a watt (or
more) into the front end of the TS830.

	If you are going to do the manual switching scheme using the A/B switch (to
select either the TS830 or TS430) and the Heathkit 6 position switch (to
select the antenna), use the best 2 position switch you can find (maximum
isolation between ports).

	Contact me via email at K5RT at Verizon.net. I have a couple of Daiwa 2
position switches in the drawer here. I'm sure we can make a deal. Be
patient, I'm going to be away for the week, but I will get back to you.

	One idea you might look into if you have the extra scratch is the Array
Solutions "Six Pack". This is a 6 x 2 antenna switch matrix, so you can use
either radio into any of 6 antennas. It has interlocks designed in so that
its impossible for two radios to access the same antenna.


Paul K5RT



> -----Original Message-----
> From: Heathkit Owners and Collectors List
> [mailto:HEATH at LISTSERV.TEMPE.GOV]On Behalf Of Bernie Arcand
> Sent: Saturday, January 06, 2007 5:20 PM
> To: HEATH at LISTSERV.TEMPE.GOV
> Subject: Coax Switching
>
>
> Hi guys...
> I have a Heathkit Coax switch that I built decades ago, and now
> that I have two rigs, I have the output of both of these rigs
> into the switch, with the common port the output to the
> tuner/antenna.  Question:  Is there a possibility or potential or
> likelyhood that by transmitting on one radio, that I can damage
> the receive on the other radio when it is turned off?  Would I
> decrease the likelyhood of damage if I turn on the RF attenuator
> on the unused rig before I turn it off?  I realize the safest way
> is to disconnect the coax and terminate it into a 50 ohm
> load...but don't want to do that.  Simply want to switch between rigs.
>
> I don't know if I was just used to the dimished receive
> capability ion my Kenwood TS830S and didn't realize it until I
> compared it to the Kenwood TS-430S, which is super hot!
>
> Just wondering what your opinions are...any and all...but rest
> assured, I'm not trading my Kenwoods for a /\/\.
>
> Bernie in ND
> WD0GMD
>
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Products bought, sold or traded here is the responsibility of the
parties involved.  This list and the City of Tempe are not responsible
for losses or misrepresentations of any kind.  Buyer beware!

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