Topband: Help With 80M Array

Tue Dec 11 18:06:24 EST 2012

When I received my box, there was a faulty soldered joint in the switch box.
It took me some weeks to find out. I was checking only my work (cable,
radials, coax length, Coax connectors....... and not checking work of
others.....well 99,9% it IS my fault when something does not work. 

See if all relays are working as they should.

You said, you sent back the RELAY box, not sure if they also checked the
SWITCH box...... ?

73 Tom  DL2OBO

PS: still looking for more FCP users for my FCP-user listing on
http://www.dl2obo.de/04b_fcp_info/fcp-info.html

-----Ursprüngliche Nachricht-----
Von: Topband [mailto:topband-bounces at contesting.com] Im Auftrag von john
battin
Gesendet: Dienstag, 11. Dezember 2012 23:02
An: wewill747 at gmail.com
Cc: topband at contesting.com
Betreff: Re: Topband: Help With 80M Array

When you switch directions do you see any (even slight) change in the swr or
power into the dummy load??? How far do you have to move the frequency
before you see power increase in the dummy load??
John
K9dx

> Date: Tue, 11 Dec 2012 16:13:09 -0500
> From: olinger at bellsouth.net
> To: wewill747 at gmail.com
> CC: topband at contesting.com
> Subject: Re: Topband: Help With 80M Array
> 
> That sounds more like relays are not being gotten voltage out at the 
> PVS switch unit. 1,2,3,G all have to be separate wires to the controller.
> Particularly suspicious like G may be mixed up with one of the 123 
> guys, which would keep any operating voltage from the relays. If you 
> had to do any cable splicing and different wire colors on the two 
> runs, that would be suspect.
> 
> 73, Guy.
> 
> On Tue, Dec 11, 2012 at 2:01 PM, Wayne Willenberg
<wewill747 at gmail.com>wrote:
> 
> > I recently bought a Comtek 2-element phased vertical array system for
80M.
> > Each vertical is ¼ wavelength in length and the 2 verticals are 
> > spaced ¼ wavelength apart.
> >
> >
> >
> > I have installed 60-- ¼ wavelength radials in a uniform and 
> > symmetrical pattern around the base of the first vertical. Using my 
> > AIM 4170 analyzer, I adjusted the length of the first vertical until 
> > the minimum SWR was at the frequency I wanted (3.71 MHz). At that 
> > frequency, the SWR was 1.4 and the series resistance at the 
> > feedpoint measured 35.7 Ohms with a series reactance of 6 Ohms. (If 
> > you are curious, the resonant frequency was 3.68
> > MHz.)
> >
> >
> > Next, I assembled the second vertical, making each section and the 
> > overall length the same as the first. I then erected the second 
> > vertical in a SW direction of the first vertical at a distance from 
> > the first vertical of ¼ wavelength. I used a transit to make sure 
> > the base of the second vertical was at the same elevation as the first
vertical.
> >
> >
> > I then installed 60-- ¼ wavelength radials in the same manner as the 
> > first vertical. Where the radials of the 2 antennas overlapped, I 
> > cut them and soldered them to a 3” piece of copper strip that runs 
> > at a 90 degree angle to a reference line connecting the 2 verticals.
> >
> >
> > To make sure the two verticals behaved the same way electrically, I 
> > connected my AIM analyzer directly to the feed point of the antenna 
> > being tested with 50 feet of coax. (The 50 feet of coax was 
> > calibrated out of the measurements.) In taking these measurements, I 
> > lowered one antenna to a horizontal position and measured the one 
> > vertical that was upright. I then reversed the process. Next I 
> > superimposed the scans of both verticals over a frequency range of 
> > 3.0 to 4.5 MHz. The traces for the SWR, Theta, and the return loss 
> > only varied slightly from each other. For example, the SWR of the first
vertical was 1.4 and it was 1.45 for the second vertical.
> >
> >
> > Next, I located the relay box, that contains the hybrid coupler, 
> > between the 2 verticals and connected the relay box to each antenna 
> > with RG-213 that is electrically ¼ wavelength long. I then ran 
> > RG-213 from the transmitter port on the relay box back to my shack. 
> > I also ran another length or RG-213 from the”50 Ohm Load” port back 
> > to a 50 Ohm dummy load in my shack. (All of the RG213 I used was 
> > new.) I also ran the control line from the 3-position control box in 
> > my shack to the rely box. Finally, I checked the continuity of all 
> > of the wiring and also made sure the relays closed or opened in response
to the signal from the control box.
> >
> >
> > After all of this effort and expense, I am very disappointed in the 
> > performance of the array. I can’t measure the RF output in the NE or 
> > SW endfire positions to determine if I am getting any gain, but when 
> > I listen to stations in Europe and switch between the NE and SW 
> > positions, I can’t see or hear any change in the signal strength. 
> > So, I question whether there is any front to back rejection.
> >
> >
> > I returned the relay box to the vendor. They checked it and said it 
> > was working correctly.
> >
> >
> > I have used my AIM analyzer to scan the feedline at my shack when 
> > the array is in an endfire position. From 3.5 to 4.0 MHz, the SWR 
> > slopes downward from 2.5 to 1.5. There is no resonant point, and 
> > Theta starts at -30 degrees and curves upward to -5 degrees.
> >
> >
> > I increased the frequency scan range and found a distinct null in 
> > the SWR at 3.4 MHz. At that frequency, Theta is 0 and the return 
> > loss is at the bottom of a very deep “V” trace and measured -36dB.
> >
> > Based on these measurements, it seems to me the mutual coupling 
> > between the
> > 2 verticals has moved the minimum SWR and the resonant point of the 
> > array, in an end fire configuration, to a point well below the 80M band.
> > *QUESTION
> > 1*: Am I misreading these results?
> >
> >
> > After reading and rereading the chapter in Low Band Dxing on Arrays, 
> > the advice is to use 75 Ohm, instead of 50 Ohm, coax for the ¼ 
> > wavelength feeders. So, *QUESTION 2*: should I try RG11 with PL-259 
> > connectors? (I use a 1.5KW amp on 80M and the maximum voltage rating 
> > for RG11 is 300V. Am I safe using RG11 or should I try LM-400-75 
> > that has a 2,000V rating?)
> >
> > *
> > *
> >
> > *QUESTION 3*: Also, is it OK to put 50 Ohm connectors (PL-259’s) on 
> > 75 Ohm coax?
> >
> >
> > *QUESTION 4:* What other tests or measurements should I try to 
> > improve the performance of this array? (I do have a dual trace 
> > scope, if that would be useful).
> >
> >
> > I’m sorry this post has gotten so long, but I wanted to explain 
> > everything I did and the measurements I made.
> >
> >
> > Thanks in advance for any help you can give me.
> >
> >
> > Wayne, KK6BT
> > _______________________________________________
> > Topband reflector - topband at contesting.com
> >
> _______________________________________________
> Topband reflector - topband at contesting.com

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