D-777 Antenna Question

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D-777 Antenna Question

Postby Dieselguzzler » Tue Apr 25, 2017 7:54 am

Morning all,

Looking for some advise/your opinions on location for mounting a D-777.
Chimney is fairly inaccessible, so my thoughts were to use a set of 18inch T&K brackets to attach to external house wall to act as a stand off to clear the fascia and guttering and mount the anttena onto the brackets.

The top of the antenna would be around 6ft lower than the chimney stack due to the fall of the roof and around 20-25ft from ground level; does this sound a valid idea?

Would the opposite fall of the roof hinder the antennas performance as it's not chimney mounted?

Anyone else using this D-777 antenna?
Equipment: UBC125XLT // WATSON W-881
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Re: D-777 Antenna Question

Postby m0lsx » Tue Apr 25, 2017 8:14 am

Anything such as roofs will always attenuate a signal, but we all have to do what we can. I for example, do not have a chimney to mount a antenna too or gable ends. So I have to mount at gutter height.
The antenna will need a pole to mount it on, so just spend a few pounds more, on a few feet more pole, to mount the antenna a few feet higher.
When fitting the T, K mounts do not forget to mount the K at the bottom & the T at the top & do not over tighten the mast to the T as it can cause the pole to snap under wind load.
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Re: D-777 Antenna Question

Postby Dieselguzzler » Tue Apr 25, 2017 8:23 am

Thanks, is that not a D-777 on the right of the picture??

Any suggestions what type of pole to buy and where from to get the antenna higher?

What's the max diameter I should be using for pole to fit u-clips
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Re: D-777 Antenna Question

Postby m0lsx » Tue Apr 25, 2017 8:43 am

Dieselguzzler wrote:Thanks, is that not a D-777 on the right of the picture??

Any suggestions what type of pole to buy and where from to get the antenna higher?

What's the max diameter I should be using for pole to fit u-clips


I use a three band 6, 2 & 70 antenna currently. Although as I have not used 2 or 70 for many years I am thinking of changing my set up.
I simply use a pole designed for TV antennas, that I brought from a local supplier.
I do not normally recommend Moonraker, but for things like poles they are fine & their postage is good. With a maximum charge of £7.99. So take a look there, as poles can be expensive to get delivered.
Aluminium masts..
http://www.moonraker.eu/poles-and-telescopic-masts/aluminium-masts

Also if you have a local supplier, a lightweight aluminium scaffold pole is good. That is what my HF antenna is mounted on.
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Re: D-777 Antenna Question

Postby Dieselguzzler » Tue Apr 25, 2017 9:09 am

Thanks for the advise, I'll look into sourcing an extra pole.

My plan was to feed the coax through the wall then fit a coax faceplate, with some coax make an "adapter lead" with one end male coax to fit into faceplate and bnc on the other end to fit onto my ubc125xlt, does this sound ok, I won't loose anything down the coax will I by using a faceplate and adapter lead onto my 125xlt?
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Re: D-777 Antenna Question

Postby m0lsx » Tue Apr 25, 2017 10:26 am

That would work. Each connector does add some loss into the system. BUT if you are using a handheld radio them you do not ideally want to feed the radio directly via low loss coax, so a tail of more flexible coax is ideally needed so that the radio can be fed easier.
However do not use too long a tail of thin coax. Especially if you want to listen to UHF signals where signals can quickly & easily be lost.
If I am using my handy on my main outdoor vertical I just lay the radio on it's side & put the radio where the coax puts least pressure onto the radios connector. But a tail makes more sense if you are using a handy all the time.
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Re: D-777 Antenna Question

Postby Dieselguzzler » Tue Apr 25, 2017 11:52 am

Is RG8 50ohm coax OK to use for all cabling including the tail from coax faceplate to ubc125xlt?
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Re: D-777 Antenna Question

Postby m0lsx » Tue Apr 25, 2017 12:50 pm

At short lengths RG-8 is fine.
However, do not assume that RG-8, or any other specification is a standard. They are not.
All coax's are not equal.
Things like Mil Spec, is a good example of how dealers & manufacturers are not honest with us. A lot of the alleged Mil Spec coax is not used by or designed to be used by, the Military.
Buy coax from good sources & remember it's no good catching a signal if you then loose a big chunk of it between antenna & radio.
An extra 50% (3dB,) on a average signal is not noticeable, but a loss of 50% on that same signal could make it disappear. And 50% is easy to loose even at VHF on under 20 meters of coax.
There are plenty of online calculators for looking at coax losses.
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Re: D-777 Antenna Question

Postby Dieselguzzler » Tue Apr 25, 2017 1:22 pm

Cheers for the info, I was considering buying all the gear needed from Radioworld @ Walsall, RG-8 works out @ £1 per mtr, your opinion?

Any other retailers you could recommend.

From antenna to location of my 125xlt would be a cable run of no more than 20mtr.
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Re: D-777 Antenna Question

Postby G4RMT » Tue Apr 25, 2017 1:47 pm

I think the world has got a bit better since RG-8. It's fairly old now, and things like Westflex 103 are quite a bit better. If budget is critical then RG-213 isn't much more than RG-8 and slightly better than the old RG-8 spec.
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