home brewing a gain master ???

[gamegetter]

-click post reply
-scroll down a bit so you can see additional options
-click on manage attachments
-a dialogue window opens so you can navigate to the file you want to attach
-there is a limit on file size and if you don't want to resize
you could host the jpegs somewhere else and provide a link to them

good luck and good day

 

[PhilipB]

[/IMG]

 

[PhilipB]

image posted

-click post reply
-scroll down a bit so you can see additional options
-click on manage attachments
-a dialogue window opens so you can navigate to the file you want to attach
-there is a limit on file size and if you don't want to resize
you could host the jpegs somewhere else and provide a link to them

good luck and good day

I think I have done it? hope this does not breech any rules or copyrights if it does Im very sorry and please remove.
Phil

 

[gamegetter]

i would think unless if you plan to market and sell product, it should not be copyright infringement, but I will leave that to the admins..

 

[Marconi]

Hi, sorry for the delay in replying hit an oil patch on the way to work the other day on my motor bike and the road won! have got a realy sore left arm and wrist.
Back to this strange antenna, all the details and plans I have from the guy in Portugal who has built and uses a home brew GM seemingly working very good even posted on youtube and had a piece in the radio user mag? I will see if I can post them up here but if not will have to link to something like photobucket as the plans are the original GM plans with his details written on them, the maths were from a directed link on the net giving the formulas for getting coax capacitance lengths (he recomends two kinds) and another link for different coax quarter wave stub matches (loads of letters and brackets which you replaced with velocity factors and desired frequency to hard for me) I have those on a scrap of paper somewhere, the 9cm one is the one the Potugese geezer used and he reports it works fine I used a different coax that was lying about.
Any clues how to post giff or jpeg up here?
Phil

Philip, consider to use the feature noted with the arrow in the image below, and you can post various type images stored on your hard drive. Just follow the instructions. Before you start make sure the image is not too large, because WWDX system has limits for the image size, so you may have to edit the image size to a smaller image before this feature, I call the "paper clip,"
will accept the image you want to post. There are a couple of steps in the process.

You also have to know where to browse in order to find your images of choice on your hard drive.

 

[gamegetter]

thanks, the measurements on the left are in meters i believe?

they convert nicely to 22.31 feet in total height, correct?

on edit: oops i meant meters not mm.

 

[PhilipB]

HB GM

Well tried to resize it but it wont? so I hope the link version earlier worked, had a word with the Mrs and she recons the given maths (online calculator) for the coax cap does not calculate to the same as info on the belden website so my coax is a POS, also she thinks the given info on the plans about the cap is suspect and unless you can guarantee the coax its all trial and error, there is also the poss. that Sirio had the coax specially made to make home fabrication that little bit harder.
I will photo the build this weekend as it is a realy good 12m antenna with a low swr with a 4 turn ugly balun on aprox 5 inch former and ll the rest the same as the plans apart from that bloody capacitor, I have tried various top section legnths but that does not help, I have tried more turns on the balun which changes nothing so I think it must be the cap, just need some good weather as its very very wet here in Northumberland.
Phil

 

[PhilipB]

HB GM

Hi guys, just been reading a thread on a physics forum called
"capacitance per foot? My foot!"
It seems there is not one clear and defined answer to this part of the build, everybody seems to have a different answer to what it is and how it can be calculated and measured correctly (apart from the dreaded Smith Chart) which I have looked at and ran away from like it was a swarm of angry killer bees:headbang seemingly my L/C meter wont give a true reading and it must be done with a low-frequency LCR meter?
I think I might try a medium sized open plate variable capacitor cable tied to the pole in place of the coax cap and see if I can pull it in to 27.500mHz that way as I am only testing with 5W.
Does anybody have any guestimates on how many volts would be pressent at the capacitor on a gainmaster with an input of 100W max at this frequency?
Phil

 

[gamegetter]

Well tried to resize it but it wont? so I hope the link version earlier worked, had a word with the Mrs and she recons the given maths (online calculator) for the coax cap does not calculate to the same as info on the belden website so my coax is a POS, also she thinks the given info on the plans about the cap is suspect and unless you can guarantee the coax its all trial and error, there is also the poss. that Sirio had the coax specially made to make home fabrication that little bit harder.
I will photo the build this weekend as it is a realy good 12m antenna with a low swr with a 4 turn ugly balun on aprox 5 inch former and ll the rest the same as the plans apart from that bloody capacitor, I have tried various top section legnths but that does not help, I have tried more turns on the balun which changes nothing so I think it must be the cap, just need some good weather as its very very wet here in Northumberland.
Phil

Your pic is visible in post #32, page 4 of this thread. Looking forward to your build photos...
I wish we could get some of your rain, we are in a drought here in the midwest of the USA.
good day

 

[gamegetter]

Hi guys, just been reading a thread on a physics forum called
"capacitance per foot? My foot!"
It seems there is not one clear and defined answer to this part of the build, everybody seems to have a different answer to what it is and how it can be calculated and measured correctly (apart from the dreaded Smith Chart) which I have looked at and ran away from like it was a swarm of angry killer bees:headbang seemingly my L/C meter wont give a true reading and it must be done with a low-frequency LCR meter?
I think I might try a medium sized open plate variable capacitor cable tied to the pole in place of the coax cap and see if I can pull it in to 27.500mHz that way as I am only testing with 5W.
Does anybody have any guestimates on how many volts would be pressent at the capacitor on a gainmaster with an input of 100W max at this frequency?
Phil

http://www.worldwidedx.com/cb-antennas/103100-1-5-kw-pep-gain-master-modification.html

attaching a link above, that you may find interesting.

 

[PhilipB]

Very interesting.

http://www.worldwidedx.com/cb-antennas/103100-1-5-kw-pep-gain-master-modification.html

attaching a link above, that you may find interesting.

Cheers Gamegetter, I have read that OP piece in the Radio User mag in the comms from europe content, very interesting apart from no actual measurements for the capacitor itself? I have posted a reply to Shockwave to see if I can get some advice.
After reading all the comments questions and answers it still seems like a smoke and mirrors situation with this strange Gainmaster antenna and they dont even have to cut it open like the A99 or Imax
"voodoo be inside that there pole"

Thanks again
regards
Phil

 

[Marconi]

[/IMG]

PhilipB, how can the length of the coil former added in at the bottom of the image above be 331,5 mm tall? The way I figure the coil height, that would make the former 13" tall. The former on my antenna is only about 5" inches. Might that dimension be 133,5 mm instead? I don't get the 149,5 and the 185,5 dimensions either, unless this antenna is maybe designed for a much lower frequency than CB or for sure if it is UK CB.

Bob85, is sometimes on this forum. He posted a thread some time back that he and a buddy were going to build a homebrew version of the GM. We haven't heard much since he posted, except he responded to a question I asked...regarding the project's status. The last word was that the antenna was over at a buddies place. Bob is in Yorkshire somewhere, why don't you try and contact him regarding what they did? Maybe an email or a PM.

I'm not surprised at Shockwave's absence since last year when that all the one-liner bullshit started toward the end of his thread. You might try and email or PM Shockwave. I don't think he minds a good conversation, but I don't think he has time for the BS...that "one-liners" :drool: around here like to interject into detail or technical type discussions.

 

[Whiplash-265]

question if i might?

looking at the above drawing for the GM...so if running something with a coax choke already incorporated into the design of the antenna, would adding one to the coax be redundant? i'm about to lift my 2012 and i believe it follows the same design element

thanx

 

[PhilipB]

HB GM

PhilipB, how can the length of the coil former added in at the bottom of the image above be 331,5 mm tall? The way I figure the coil height, that would make the former 13" tall. The former on my antenna is only about 5" inches. Might that dimension be 133,5 mm instead? I don't get the 149,5 and the 185,5 dimensions either, unless this antenna is maybe designed for a much lower frequency than CB or for sure if it is UK CB.

Bob85, is sometimes on this forum. He posted a thread some time back that he and a buddy were going to build a homebrew version of the GM. We haven't heard much since he posted, except he responded to a question I asked...regarding the project's status. The last word was that the antenna was over at a buddies place. Bob is in Yorkshire somewhere, why don't you try and contact him regarding what they did? Maybe an email or a PM.

I'm not surprised at Shockwave's absence since last year when that all the one-liner bullshit started toward the end of his thread. You might try and email or PM Shockwave. I don't think he minds a good conversation, but I don't think he has time for the BS...that "one-liners" :drool: around here like to interject into detail or technical type discussions.

Sorry cant help there as I have already quoted prviously the plans are from a kind ham/cber in Portugal who has reported to have built and uses this antenna which he finds better that others he uses? cant comment on the validity of such info as I dont know him and have never been to Portugal.
I think it refers to the actual coax length in the coil not the coil hieght as that would as you point out be a bit silly and the coax at 16 turns would be very very heavy duty.
New info on my feeble atempt, tried the open plate variable cap and fully unmeshed it came in at 15m? swr hardly mooving the needle with CW and PSK31 comming in strong with nearly no noise, its a strange and wonderull thing this design it must have cost Sirio a packet in reseach and development but as I am disabled and only working part time (no benefits claimed at all) I cant afford to purchase one or I would in a heartbeat, not many antenna work well here at this horrible qth (deep river valley with hillside woodland) and so far this one sounds the best Ive tried on the bands Ive pulled it in on, it is only 6 feet off the ground in the brolly hole on the patio/garden table.
Please note using cheapest components and only looking at low power use so It will be a lot of trial and error, only wish I was an anntenna guru with one of those fancy analizer gizmos.
Phil

 

[PhilipB]

Ugly Balun

question if i might?

looking at the above drawing for the GM...so if running something with a coax choke already incorporated into the design of the antenna, would adding one to the coax be redundant? i'm about to lift my 2012 and i believe it follows the same design element

thanx

Sorry whiplash I cant help at all with that one:blink: but I did have to put one on the bottom of my comtell 444 (same as sigma4) when I had it due to massive tvi problems and it worked well, no more tvi, lower swr and a slightly better bandwith? dont know how it worked but it did, used the same former as Im using now on HB GM which I will be posting pics of soon when I can work out how to reduce size/quality on my digi camera.
regards
Phil