[Hi-zreceivingarraydiscussions] Hi-zreceivingarraydiscussions Digest, Vol 19, Issue 4

Thu Sep 20 12:58:54 EDT 2012

You can eliminate parasitic effects by eliminating ALL 1/2 wave (or close) equivalent circuits coupled to the antenna. For example, a 1/4 wave vertical, L network, coaxial line together with the ground system will "look' like a 1/2 wave parasitic element. Switching the bottom of the antenna (via a relay) out of the circuit will eliminate the parasitic effects as a 1/4 wave conductor by itself has little effect. Shorting the antenna to ground is NOT A GOOD IDEA, as it may create an excellent parasitic element...much better to open up the base. IN the unlikely event you are using a 1/2 wave vertical, you will need to detune it by inserting a capacitor or inductor to ground to detune the resonant frequency. Assuming the inverted L is an equivalent 1/4 wave, simply switching the antenna base off the base tuner will do the job. Towers with grounded bases can be very difficult if the tower is near electrical 1/4 wavelength (about 100 feet high with antennas) for TB.

If you are using a short antenna (like 1/4 wave), you can use a heavy open frame relay instead of a vaccuum relay, since this will be a low Z point (high current, but low voltage), but seal it up against bugs and weather. 

Also, an exellent cost effective substitute for vaccuum relays is offered as Russian surplus: http://www.nd2x.net/ur4ll.html Dr. Alex is a good guy.

RF Relay >1000 W (for HF) open-frame relay, 24-27VDC coil (use for HV, e.g. 3kV 2A is no problem; NOTE:  20A at 30 MHz ) - $15
Plate with two installed - $30
Plate with four installed - $60 

+ shipping from the Ukraine.

I've used these relays for several years and they are every bit as good as vaccuum for high RF voltages and currents. The relay coils consume about 500 mA each, so you'll need a hefty control supply. Buy several to make it cost effective with shipping....these are like gold for heavy RF switching.

Bob Zavrel, W7SX

> From: hi-zreceivingarraydiscussions-request at hizantennas.com
> Subject: Hi-zreceivingarraydiscussions Digest, Vol 19, Issue 4
> To: hi-zreceivingarraydiscussions at hizantennas.com
> Date: Thu, 20 Sep 2012 12:00:09 -0400
> 
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> Today's Topics:
> 
> 1. Detuning antennas when using 4 square (Doug Turnbull)
> 2. Re: Detuning antennas when using 4square (kd9sv)
> 3. Re: Detuning antennas when using 4square (Roger D Johnson)
> 
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Wed, 19 Sep 2012 20:14:36 +0100
> From: "Doug Turnbull" <turnbull at net1.ie>
> To: <hi-zreceivingarraydiscussions at hizantennas.com>
> Subject: [Hi-zreceivingarraydiscussions] Detuning antennas when using
> 4 square
> Message-ID: <D4F87494AC9643FE8396A4C2A5527327 at DOUG1>
> Content-Type: text/plain; charset="us-ascii"
> 
> Gentlemen and Yls, 
> 
> I am using a Hi-Z four square and find that then my 160M inverted L
> is down that it works better on both TB and 80M. Obviously there is an
> interaction and yes it is certainly closer than two hundred feet to the
> closest point of the 4 sq. What method of detuning antennas such as the
> inverted L is normally used? I suppose a relay switching in or out is
> part of the system and the problem then becomes that when operating on TB
> the TX antenna must be detuned possibly slowing down operations and if not
> properly thought out problematic for a power amplifier.
> 
> 
> 
> I am most pleased that Hi-Z is again actively trading. The product
> is good and the service of equal value. Long may this company be with us.
> 
> 
> 
> 73 Doug EI2CN
> 
> 
> 
> ------------------------------
> 
> Message: 2
> Date: Wed, 19 Sep 2012 15:30:16 -0400
> From: "kd9sv" <kd9sv at comcast.net>
> To: "'Hi-Z Receiving Array Discussions'"
> <hi-zreceivingarraydiscussions at hizantennas.com>
> Subject: Re: [Hi-zreceivingarraydiscussions] Detuning antennas when
> using 4square
> Message-ID:
> <mailman.8.1348156809.16610.hi-zreceivingarraydiscussions_hizantennas.com at hizantennas.com>
> 
> Content-Type: text/plain; charset="us-ascii"
> 
> Doug, I would use an RJ-1A vacuum relay to open (disconnect) the antenna
> from the feedline...if no current can flow in the antenna wire it should not
> re-radiate and bother the 4 square...de gary
> 
> -----Original Message-----
> From: hi-zreceivingarraydiscussions-bounces at hizantennas.com
> [mailto:hi-zreceivingarraydiscussions-bounces at hizantennas.com] On Behalf Of
> Doug Turnbull
> Sent: Wednesday, September 19, 2012 3:15 PM
> To: hi-zreceivingarraydiscussions at hizantennas.com
> Subject: [Hi-zreceivingarraydiscussions] Detuning antennas when using
> 4square
> 
> Gentlemen and Yls, 
> 
> I am using a Hi-Z four square and find that then my 160M inverted L
> is down that it works better on both TB and 80M. Obviously there is an
> interaction and yes it is certainly closer than two hundred feet to the
> closest point of the 4 sq. What method of detuning antennas such as the
> inverted L is normally used? I suppose a relay switching in or out is
> part of the system and the problem then becomes that when operating on TB
> the TX antenna must be detuned possibly slowing down operations and if not
> properly thought out problematic for a power amplifier.
> 
> 
> 
> I am most pleased that Hi-Z is again actively trading. The product
> is good and the service of equal value. Long may this company be with us.
> 
> 
> 
> 73 Doug EI2CN
> 
> _______________________________________________
> Hi-zreceivingarraydiscussions mailing list
> Hi-zreceivingarraydiscussions at hizantennas.com
> http://mail.hizantennas.com/mailman/listinfo/hi-zreceivingarraydiscussions_h
> izantennas.com
> 
> 
> 
> 
> ------------------------------
> 
> Message: 3
> Date: Wed, 19 Sep 2012 15:58:44 -0400
> From: Roger D Johnson <n1rj at roadrunner.com>
> To: Hi-Z Receiving Array Discussions
> <hi-zreceivingarraydiscussions at hizantennas.com>
> Subject: Re: [Hi-zreceivingarraydiscussions] Detuning antennas when
> using 4square
> Message-ID: <505A23F4.6080105 at roadrunner.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> 
> It's a bit more complicated then that. If you open the feedline center conductor
> at the antenna (Ithink that's what you mean), you still have two half waves on 80m.
> Also, you have the combined length of half the inv V and the outer conductor of the
> feedline that's resonant somewhere! Doug..do you have a good balun to prevent
> this?
> 
> 73, Roger
> 
> 
> 73, Roger
> 
> On 9/19/2012 3:30 PM, kd9sv wrote:
> > Doug, I would use an RJ-1A vacuum relay to open (disconnect) the antenna
> > from the feedline...if no current can flow in the antenna wire it should not
> > re-radiate and bother the 4 square...de gary
> >
> > -----Original Message-----
> > From: hi-zreceivingarraydiscussions-bounces at hizantennas.com
> > [mailto:hi-zreceivingarraydiscussions-bounces at hizantennas.com] On Behalf Of
> > Doug Turnbull
> > Sent: Wednesday, September 19, 2012 3:15 PM
> > To: hi-zreceivingarraydiscussions at hizantennas.com
> > Subject: [Hi-zreceivingarraydiscussions] Detuning antennas when using
> > 4square
> >
> > Gentlemen and Yls,
> >
> > I am using a Hi-Z four square and find that then my 160M inverted L
> > is down that it works better on both TB and 80M. Obviously there is an
> > interaction and yes it is certainly closer than two hundred feet to the
> > closest point of the 4 sq. What method of detuning antennas such as the
> > inverted L is normally used? I suppose a relay switching in or out is
> > part of the system and the problem then becomes that when operating on TB
> > the TX antenna must be detuned possibly slowing down operations and if not
> > properly thought out problematic for a power amplifier.
> >
> > 
> >
> > I am most pleased that Hi-Z is again actively trading. The product
> > is good and the service of equal value. Long may this company be with us.
> >
> > 
> >
> > 73 Doug EI2CN
> >
> > _______________________________________________
> > Hi-zreceivingarraydiscussions mailing list
> > Hi-zreceivingarraydiscussions at hizantennas.com
> > http://mail.hizantennas.com/mailman/listinfo/hi-zreceivingarraydiscussions_h
> > izantennas.com
> >
> >
> > _______________________________________________
> > Hi-zreceivingarraydiscussions mailing list
> > Hi-zreceivingarraydiscussions at hizantennas.com
> > http://mail.hizantennas.com/mailman/listinfo/hi-zreceivingarraydiscussions_hizantennas.com
> >
> 
> -- 
> Remember the Liberty (AGTR-5)
> http://www.usslibertyveterans.org/
> http://www.gtr5.com/
> 
> 
> 
> 
> ------------------------------
> 
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> End of Hi-zreceivingarraydiscussions Digest, Vol 19, Issue 4
> ************************************************************