CB RADIO: Sirio Gain-Master Repair / Re-build 11 & 10 Metre bands
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- čas přidán 29. 08. 2024
- CB RADIO: Sirio Gain-Master Repair / Re-build 11 & 10 Metre bands.
Yesterday my Sirio Gain-Master stated to give me some pretty high VSWR readings, so I guess it was time to get it down from the roof and see what is going on!.. Please join me in this look at the Gain-Master a brilliant 11/10 metre CB antenna.
www.sirioanten...
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Cheers
Mike - M0MSN
P.S. do not take my word for it, give it a go for yourself.
I tried this antenna over the sirio 827 it was on the mast for 1 day then taken down and the 827 back up- the gainmaster turned into a horizontal dipole in the wind. Nice tidy job you made of that repair.
The 827 is the go to antenna in my book, had that up for many years prior to the Gain-Master, problem was the birds also love the 827 to perch on.
Nice repair ! . looks like you can use it on 12 meters as well. nice bandwidth ! The Gain master is still made new. Moonraker sells them. love the gain on them ! it's the 5/8 wave T2LT antenna. I made a 1/2 wave T2LT antenna out of RG 8X and a plastic bottle about 65 mm for the coil with the ends cut off so I can slip it over the 10 meter DX commander pole and up with a piece of shock cord at end to hold it in place . go a usable tune 11 and 10 meter . makes a great portable antenna . takes 500 PEP watts with SWR 1.5 or less. even made one for 6 meters . next one I make is for 15 meters . will need longer pole. I watched both 1/2 wave T2LT and 5/8 wave T2LT video's on this you tube channel. their is a outher option for coil . wrap a ferrite FT 240-43 or mix 31 for the coil . with the RG 8X . would like to make the 5/8 wave one. have to get the matching stub coax. I have every thing else. I have M & P hyper flex 5 and 7 . should work fine. 73's
Ah.. You did it Mike. Good job.. I am wondering if you would do the same again if you made one completely out of wire, like you did for me old boy? Let's discuss!
Glad to see you replaced that red coax with black jacketed coax, as I always thought the red stuff wouldn't be as UV resistant.
thanks for the inspiration - saw the video on sunday and yesterday i finally managed to understand how the three matching components (capacitor, transmission line, stub) work together by simulation in mmana and Will Klesey's online smith chart tool. Thinking about building one for 20m ... 73 de db3mi
20M that is going to be a big antenna.. good luck
@@mike-M0MSN as it´s pretty broadband a 20m version should fit perfectly on a 13,7m fibre pole. thanks, 73
Yep that's the length I worked it out to be @@db3mi so you would need a 15M pole so you could mount it ( Callum has some 18M poles) cheers
May I know how to calculate length for stub ?
@@davidchien0327 85x velocity factor by the coax cable you use for the matching stub. 73 from Germany
I have pulled a few Stationmaster, Itron and Megatron antenna's apart over the years myself. It NEVER ceases to amaze me that the part that is "factory sealed" is always the part with the MOST corrosion, I doubt ANY of these older antenna's were ever really waterproof, or even water resistant, I remember drilling a 6mm hole in the bottom of my own Megatgron antenna and watched about 500ml of sludgy, icky water drip out over a short period, it did drop my SWR from 1:4 down to 1:1.2, I wonder how badly corroded it actually was inside, I never fully pulled that one apart.
Yes it alway amazes me just how the manufacturers make their antennas. Are they made to last or is there an expiry date??
Brilliant I really enjoyed this glad it all worked out
I've been thinking about rebuilding my 5/8 Gainmaster to be able to withstand more than 500w, why the factory engineered it for 500w max is anyone's guess!
Great video, thanks for sharing!
Mike I'd have just run a tap where you cut off the crimped part of the SO239... Just like the mobile version that sirio sell.
Great video brother. Very enjoyable.
Ash.
Good tip! Thanks 😊
Love to see you build a weather satellite receiving antenna
Great video 🙂
Thank you 😁
about to rebuild mine as it has gone a bit deaf (very deaf now as in bits) and shows water ingress lots of it showing on the braid.
when taken apart found loads of pinch points on the coax where the coil starts and just inside the antenna before the first stub.
going to rebuild it in the week like the way you have and get it back up.
It’s a great antenna good luck with the rebuild.
Good vid Mike, I might scale that down to build one for 6m or 4m, keep up the good work, Keith 2E0XSZ
That’s a great idea, may do that myself.
Remind me next time you see me, I have some Graphite grease we use on the Heliax Earthing Kits
Will do
check the connection beetween the koax and the singel top wire, got that issues on some of my homebuilt GM..
When U got a break there the SWR risa up to 3-4 something..
Cheers de sm3tek
What coax did they use for the matching stub. It looks smaller tha Westflex 103 you had in your other Gainmaster videos. Great video. Have learnt a lot from you.
Nice restoration and well done! Could you measure the velocity factor of the original orange coax used by Sirio?
Yes, absolutely. However using the lengths of the original parts against the lengths of the replacement parts RG58, I worked out that the original coax VF is around 76% .
VERY curious how it loads on 15, 17 or 20? The A99 and M2000 load well on 15, and17 ? Seems I read Gain-Master snap somewhere around the coil , a small pvc pipe over that area might stop that?
Nicely done as always Mike. That gives you a broad, usable bandwidth. I'm not familiar with the Gainmaster, so presume your version has better bandwidth? Best 73 Ace G0ACE
It’s about the same bandwidth it just starts slightly lower down than the original, I could shorten the antenna but if it works 😉
@@mike-M0MSN ... don't fix it!! Thanks Mike.
Very good nike congratulations PU2 WRE WILSON BRASIL
Thank you.
Hello Mike,
great job your repair at GM5/8. How long is the original capacitor (the shield from coax)? The coax looks like PTFE-coax high voltage RG142, 303, 400 95 - 96pF/m. 73 from Germany.
8.5cm length Coax Cap is 8.6pF (RG142)
Thank you very much. 73 Marko 13RF787 13HN980
Iam surprised that brand of antennas were good this is a first😮
The brand is good, I am to blame for the problems here, the idea is you only put it up once and it will stay working for years, but I keep putting the antenna up and down and overtime I have weakened the coax joints and connectors
Hello Mike. A general question and observation. I noticed on your unun making 49-1 etc you connect the twisted wires to eyelet and single wire to connector inner. Many unun I have purchased have twisted wires to inner inner of coax connector as its start of windings. I also make mine this way. But tried both ways and it doesn't make a difference I cam measure. Which is correct. Cheers from G1BKI mick (George)
Both will work, voltage or current is the difference..
Could an ordinary capacitor be used? Sorry if its a silly question for some. And why the different coax for the matching?
A special high-voltage capacitor is quite expensive, which is why it is made this way. Price reduction.
Of course you can use any high voltage capacitor for several thousand volts.
17:49 I've read that the capacitor is the weakest point, when it comes to the maximum power of the aerial. Do you think changing it for a higher working voltage one would work?🤔
Yes possibly let me know if it works
The limiter of power at the RG58 coax (better is it to use Belden H155 PE) centerfeeded 5/8 dipol is the matching stub an capacitor, for the stub is it better to use RG213, Westflex W103, RG142, 303, 400 and for the capacitor RG142, 303, 400. 73 from Germany.
Im struggling to source westflex, would it be possible to use rg213 as a matching stub?
yes, but the length needed will be different ( you will have to find the length needed by trying it)
Is the BOTTOM of the top section of coax shorted where it joins the braid of the "capacitor"? And what would you need to do to get the antenna to be usable in the 12M band (shift the resonance lower)?
There is no shorts in this antenna until you short the end of the matching stub. The top section of the antenna is a DC block the centre core of the coax is connected to one side of the capacitor and the driven element is connected to the other. To make it useable on 12 you simply need to scale it up.
Hi Mike,
Do Sirio use RG58 on the bottom choke?
No they are using a higher velocity coax.
It's like Belden H155 PE.
hi can you help whit grinding setup
God built cheap wow.