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 SWR Meters & ATU's for VHF 
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Post Re: SWR Meters & ATU's for VHF
The main effect of having it near the HF antenna like that will be to lower the major lobe angle, which may or may not be an advantage. (compared to having it in the same position without the HF antenna there)

It will also affect the gain, resonant frequency and F/B ratio, though those effects can be nearly designed out.

One saving point is that you will be able to adjust the SWR of the 2m beam reasonably well fairly low down, even with the tower tilted if that is what it does.

It will still be worth doing, even if not ideal.


Fri Dec 02, 2016 4:36 pm
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 SWR Meters & ATU's for VHF 
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Post Re: SWR Meters & ATU's for VHF
People have been running (working upwards) tribander, 2m Yagi and co-linear on the same stub for donkey's years with no problem.

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Fri Dec 02, 2016 4:41 pm
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Post Re: SWR Meters & ATU's for VHF
Ive got a similar situation and take the view its better to have something up there working to say 80% capability rather than nothing.
In practice I've got a 3ele HF yagi at the bottom of the stubmast,a 10ele 2M horizontal yagi about 1.5mtrs above that,and a pair of 20ele horizontal 70cms yagis stacked around 1,5metres above that.
I can honestly say I've not noticed any great problem,the Dutch beacon is about as loud as its ever been on 2m,furthermore 70cms seems to work about as well as it did with 4x21ele tonnas all by themselves.
I also use Bird 43's to measure power,Ive also got a Welz Sp300 and an Sp400 I use occasionally.
I look forward to working you on 2M Ray :D


Fri Dec 02, 2016 4:56 pm
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Post Re: SWR Meters & ATU's for VHF
Hi Tony
Thanks for that link on stacking, very useful.
I will check the feeder up the tower to the collinear as it might be the problem. I use a Array Solutions Ratpak antenna switch at the base of the tower and other antennas from that switch seem fine, so I think the feeder to the tower from the shack is OK. The problem mainly seems to be on TX as I receive sigs from other locals on 2M OK. As I said, on 2M CW they give me a 519 when I am receiving them at say 579. I will also have to check out the rig I'm using on 2M, - a SunSDR2PRO
When I said the locals are using Verticals, I meant the locals on a local CW net, who may well be different from those you contact.
I just getting a 2nd hand 100W 2M Microset linear, which in conjunction with the 9-el beam should sort out my problem.
Thanks for the help

73 de Ray G3XLG

gw8asd wrote:

It sounds as if you have a problem there.
I wonder what sort of feeder you are using?
How do TX and RX reports compare? Is the problem mainly on TX, I wonder.

I'm surprised you say most of your locals are using vertical for CW/SSB, they're certainly not the ones I work from here, and I would suspect that they are not very successful.

The 9ele will probably be fine, but not ideal, at 2mtrs above your HF antenna.
I suspect it will be fully in the capture area of the HF antenna.
http://www.ifwtech.co.uk/g3sek/stacking/stacking2.htm

You're about 300km from me so, with 100W, you should be a reasonable signal especially if you are on a high spot.
There are a couple of stations reasonably local to you who are regulars up here.

Cheers

Tony


Fri Dec 02, 2016 5:05 pm
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Post Re: SWR Meters & ATU's for VHF
G3XLG wrote:
Hi Tony
Thanks for that link on stacking, very useful.
I will check the feeder up the tower to the collinear as it might be the problem. I use a Array Solutions Ratpak antenna switch at the base of the tower and other antennas from that switch seem fine, so I think the feeder to the tower from the shack is OK. The problem mainly seems to be on TX as I receive sigs from other locals on 2M OK. As I said, on 2M CW they give me a 519 when I am receiving them at say 579. I will also have to check out the rig I'm using on 2M, - a SunSDR2PRO
When I said the locals are using Verticals, I meant the locals on a local CW net, who may well be different from those you contact.
I just getting a 2nd hand 100W 2M Microset linear, which in conjunction with the 9-el beam should sort out my problem.
Thanks for the help

73 de Ray G3XLG



The Array Solutions Ratpak seems to be an HF, up to 6M, unit with crude relays so attenuation at 2M is an unknown quantity.
Have you measured the losses?

What feeder are you using to the switch, and what after?
That can make a huge difference.
I aim for 1dB, or less, loss between equipment and antenna.
So it's 1/2" hardline, to the mast base, and Ecoflex 15 over the bendy bits to the antenna, no switches.

Cheers

Tony.

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Fri Dec 02, 2016 9:12 pm
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Post Re: SWR Meters & ATU's for VHF
Rat pack switch will cause SWR issues on two meters, they don't recommend it's use there as others have found issues.

http://www.eham.net/ehamforum/smf/index ... 594.0;wap2

Relates to six meters, but comments on two meter performance half way down.

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Fri Dec 02, 2016 9:44 pm
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 SWR Meters & ATU's for VHF 
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Post Re: SWR Meters & ATU's for VHF
Looks like I now have a lot of work to do here!

I've checked out the specs on the RatPak and as has been said, its only for HF use upto 6M & causes SWR probs on 2M and above, so that will have to be taken out of the circuit for 2M.

Currently the line to the mast base is about 25M of Westflex 103 with an estimated attenuation therefore of 1.5dB, then through the suspect Ratpak switch, and then up the mast with about 21M of Messi & Paoloni Utraflex 7 to the collinear, with an estimated attenuation of a further 1.5dB.

I already have a new 100M coil of LDF4-50A hard line which I was going to install from the shack to the mast base RatPak for both HF & VHF, so I now think I need to put in two separate lines to the mast, one for HF & one for VHF. Then I could replace the 21M of Ultraflex 7 with 21M of either Ecoflex 15/M&P Ultraflex 13. These two transmission line improvements should have the effect of reducing attenuation between the shack & the antenna from at least 3dB to less than 1.5dB.

I really appreciate the very helpful advice & ideas that I received in this thread & look forward to a vastly improved performance on 2M in the future.

73 de Ray G3XLG


Sat Dec 03, 2016 3:31 pm
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Post Re: SWR Meters & ATU's for VHF
G3XLG wrote:
Looks like I now have a lot of work to do here!

I've checked out the specs on the RatPak and as has been said, its only for HF use upto 6M & causes SWR probs on 2M and above, so that will have to be taken out of the circuit for 2M.

Currently the line to the mast base is about 25M of Westflex 103 with an estimated attenuation therefore of 1.5dB, then through the suspect Ratpak switch, and then up the mast with about 21M of Messi & Paoloni Utraflex 7 to the collinear, with an estimated attenuation of a further 1.5dB.

I already have a new 100M coil of LDF4-50A hard line which I was going to install from the shack to the mast base RatPak for both HF & VHF, so I now think I need to put in two separate lines to the mast, one for HF & one for VHF. Then I could replace the 21M of Ultraflex 7 with 21M of either Ecoflex 15/M&P Ultraflex 13. These two transmission line improvements should have the effect of reducing attenuation between the shack & the antenna from at least 3dB to less than 1.5dB.

I really appreciate the very helpful advice & ideas that I received in this thread & look forward to a vastly improved performance on 2M in the future.

73 de Ray G3XLG

Looks as it you'll be going along the right lines.
I've about 20mtrs of 1/2" Cu2Y (similar to 450) from shack to base of tower.
About 20mtrs of Ecoflex 15 up to the masthead preamp and about 2M of Ecoflex 10 from there to the antenna.
Around 1dB of loss is what I aim for.

Cheers

Tony

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Sat Dec 03, 2016 3:37 pm
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