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Setting up a Sirio Gain Master, have questions!

K

K7RDN

Member
Dec 2, 2010
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I have ordered a GM and trying to get all the components to install it but I have a few questions.

At this point I will be installing the GM on a Rohn 9H50 on top of my roof, thanks to the encouragement of CDX-007. Is there any SWR adjustments on the GM? Do I need to ground the antenna or mast? Does the GM or just the mast need to be grounded? If just the mast, can it be grounded from the bottom of the mast or do I need to go to the top? What gauge copper wire do I need for grounding or can I use the more flexible braided grounding strap? If I need to attach at the top of the mast or GM, how do I secure it coming down the mast?

I think I am going to get some LMR 400 coax, do I need to loop it at the bottom of the GM so there is not any pull or stress on the PL-259 connector? How do I secure the coax to the mast? I am trying to find the 5/16" Dacron covered Kevlar but haven't been able to locate any. If anyone knows where I can order some please let me know.

Any other suggestion would be greatly appreciated!
 

Hi Bob, Here's where my friend Phil just bought his, not cheap but strong and RFI-Free! Rope

No SWR adjustment will be necessary, it's all done, just plug-n-play!

Use electricians tape liberally to hold the LMR400 (excellent choice!) to the mast about every 5-8 feet, and I use liquid electrical tape to seal it from the elements wherever I have a connector.

As far as grounding, you should always have a good station ground to the radio & amp, and I suppose the mast could be grounded, might help the SGM see a better ground on the shield through the mounting tube.

Glad you accepted the challenge, you're going to have quite the performing station there!

Once licensed you might want to look into one of these. - After all, how many times do you see NINE PAGES of reviews and still it has a 5 out of 5 rating!?!?!

icom-751a.jpg


Full rich audio, frequency stable, receiver selectivity like a brick wall, and as sensitive as anything I've set alongside it, including an FT-1000MkV MP, FT-1000D, FT-990, TS-940SAT, TS-930S, IC-761, IC-746, etc...
 
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I've been thinking about getting my license. Even picked up a couple of books to prepare me for the test but just haven't done it yet. After getting setup at home again I'll have to devote some time and get it.

Thanks for the link on the guy wire. I imagine I will have to support the fully extended mast (34') in about 3 places, correct?

Glad to hear there is no SWR tuning to do. Makes it a whole lot easier to put up.

Should I leave a little slack in the coax where it attaches to the SGM? Does the SGM have a grounding connection on it or just ground the mast?
 
Bob it just grounds to the mast via the mounting tube & brackets.

Leave a little slack in that you don't want it pulling the coax down or sideways from the connector, but an inch of 'easy bend' is fine.

The way I've installed telescoping masts from my teens on is to set the base bracket and the bottom 4 directions of guy lines, (it helps to use a 3'-6' level) and then I use a 12' fiberglass A-frame ladder which I can leave in place when I find an antenna that needs tuning on the mast, since it's fiberglass it won't affect the tuning.

I recommend you guy it 3-4 directions at every section.

If it's a 34' then I presume it uses 4 sections, so you'll probably want to use at least 8 eye bolts, 2 per corner, 2 guy lines per eye bolt, and guy all 4 sections up to the base of the SGM.

I've also had to 'Wing-it' when I don't have my A-frame ladder by using a shorter (16') extension ladder and balancing it up against one side of the mast at the 10' level with a leg on each side of the roof crown, and I will wrap guy line from the mast to each leg to prevent it from sliding or walking out, and a line from each side of the top of the ladder to the mast to keep it from sliding left or right.
This way is more anxiety inspiring but I haven't come off a roof (or gone through one) yet!
- There but for the grace of God go I... :mellow:

Be careful and intelligent about it and you shouldn't have a problem. If you have any friends with experience in this field add a one-day rider to your home owner's insurance and bribe them with steak and brewskies to come and help!
Make sure the brewskies are for AFTER the installation! ;)
 
I am planning on using a 4 point guy wire tie down. Looking at the mast and the factory recommended guy wire points, there are 5 point on the mast shafts to put guy wires, that means 20 different guy wires! I can see that this is going to get costly for guy wire (rope). With regular 6 strand, 18 or 20 gauge guy wire, you mentioned that I would have to use insulators on the guy wires, how many per wire and how far apart? Would I have to do all guy wires, referring to the very bottom guy wires?
 
Bob, I was thinking about your 34' mast, isn't that a 4 x 9' mast? If so, you should have a guy ring at the top of each mast section, so 4 guy rings or guy points.
I suppose you could guy the top 2 sections, and of course the bottom section, and ignore the 2nd one up since most of the wind loading should be at the top.

The bottom guy lines support the base section, beginning it all level & plumb, and since the SGM is a very minimal wind load I don't see any issues arising from only guying the most critical 3 of 4 guy points, unless you could figure a way to lower the 3rd guy ring down from the top to the center of the 3rd section, then it would be more symmetrical and use a little less guy line. I would expect a single 500' roll of the 1/8" should do it just fine, and if needs be, use metal guy wire for the base, it's well below 18' beneath the SGM and shouldn't require insulators.

If you decide to use insulators you'll be in for at least $35-$50 just for the insulators, those little bastages are getting pricey!

On each guy wire I'd do one about 2" from the guy ring, then another every 5'-6' until it was well below 18' beneath the SGM.

It's really a hassle to wrap all those insulators and keep the guy wire from getting tangled, you might want to give the 'Kev-ron' more consideration.

Hurry up and get it playing, I wanna hear it!!
icon12.gif
 
Unbelievable.

My 1950's Rohn 5 section telescoping mast is 5 14g 10' sections, 47' total with 9" overlap at each of the top 4 sections.

I had it at 45' (15" overlap) all those years I was in high school for a little added strength.

Now I'm sorry I gave away my last brand new $79 5 section which was 8', 8.5', 9', 9.5' & 10' of 16g throughout, for 42' total extended height.
(9" overlap each)

Are you certain you couldn't walk your neighborhood and find someone who will give you their oldie but goodie 4 section, just for taking it down for them?
At least most of those would give you 36'.

I wouldn't hesitate to do the bottom, middle and top sections with only an SGM on top. If it were an I-10K I'd guy all 5.

...I'm stunned at what's happened to almost everything, cheapened and shrunk while the price goes through the roof! :censored:
 
I am ordering this one because it can be shipped UPS for about $54 and the regular H50
ROHN H50 Telescopic Push Up Antenna Mast

shipping cost is like $150. The H50 total extended length is 43 feet. I think that 50-54 feet off the ground to the bottom on the SGM should be plenty, especially since at first it was only going to be about 30' mounting it on a gable wall.
 
So you think the 1/8" Kevlar will be strong enough for this mast? What kind of clamps do you use with it? I know I will need some turn buckles.
 
Hey Bob,

OK I guess I took that wrong, so I see they make that mast with shorter tubes to fit in elevators and shipping containers.
The one in that last link is the one I gave away last year :headbang

The 1/8" will be incredibly strong, enough to steady my friend's 40' tower sporting a 5 element tri-bander!

- Remember, kevlar vests stop bullets.

I believe they may offer some type of clamp system, call & ask what they recommend.

I've only used the kite string size and my 365lb friend John and I (245lbs) both pulling on it tied between two socket extensions couldn't break it, and the 1/8" is much larger & stronger. 'Overkill' would be the correct term.

2-3 strands of the 1/8" could probably tow a car. (y)
 
I've been using 3/8" Dacron covered polyether for 15 years and I've never had a problem, even when adding extra line and using good solid knots to tie together. It is not as small as a similar strength Kevlar, it too doesn't have hardly any stretch, and it is at least 1/2 the price. I don't even notice it stretching due to the heat of a very hot day in Texas while my coax, on-the-other-hand stretches like you wouldn't believe.

I got 1000' feet for a bit less than $100 shipped as I recall.

Synthetic Textiles Inc* www.synthetictextilesinc.com
 
The 9H50 mast has 5 guy wire location on the mast. Approximately 6', 13', 20', 27' and 34'. I thought I would guy wire the top 4 sections with 4 guy wires each. If I needed to attach guy wires on the bottom section (6') that would be easy enough to do at a later time by myself. With these numbers is looks like I am going to need about 600', about $110 plus shipping. Then I'm going to need a turnbuckle for each guy wire, about 16. Will these work for that?

Amazon.com: National Mfg Co 5/16X9 Turnbuckle N221-754 Turnbuckles: Home Improvement

I figured on Eye Screw for every 2 guy wires, 8 total.

National Manufacturing Co N220-798 5/16x4 Stainless Steel Lag Screw Eye - Hardware & Farm - Spring Hook Eye & U Bolt - Screw Eye Stainless
190 LBS capacity

or these:

National Manufacturing Co N220-806 3/8x4-1/2 Lag Screw Eye - Hardware & Farm - Spring Hook Eye & U Bolt - Screw Eye Stainless
275 LBS capacity
Any suggestions?
 
Think in 'worst case' scenarios. Those items would work fine for tensioning a screen door, but not for a 30 - 35 foot mast subject to the usual variations in weather. So, no, they won't work for very long. Maybe fine on a calm day. Listen for loud, ugly sounds on a windy day. Sorry 'bout that.
- 'Doc
 

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