home brewing a gain master ???

[PsiDOC]

I couldn't agree more Northern.
However the design I have used here uses RG58 for the capacitor as well hence I recommend 120 125 watts maximum for the RG58 based design I have posted.

Psi

 

[Shockwave]

I think the point is being somewhat lost, it has already been established that the capacitor and tuning stub benefit from a lower loss cable, that isn't being questioned, however the feed, and the rest of the antenna shouldn't suffer with most installations, IIRC the original Gainmaster was rated at 500W, but many failures of the capacitor were reported at powers less than this.

It's worth noting that all of the reported failures we have seen online were from the very first production run. Improvements have been made to the capacitor that seem successful in that the failures appear to be non existent now.

 

[northern35s]

It's worth noting that all of the reported failures we have seen online were from the very first production run. Improvements have been made to the capacitor that seem successful in that the failures appear to be non existent now.

What was the fix (to save me searching the web )

 

[Shockwave]

What was the fix (to save me searching the web )

If you look at the pictures of the early failures you will see the coaxial capacitor arced at the cut end of this wire. On the first production run the wire was cut flush on the end. Making it very easy to arc between the center conductor and outside braid. Now the end is prepped so the center Teflon insulation extends just beyond the braid and easily handles the full breakdown voltage of the cable without the arc on the end. Simple yet effective fix.

 

[northern35s]

If you look at the pictures of the early failures you will see the coaxial capacitor arced at the cut end of this wire. On the first production run the wire was cut flush on the end. Making it very easy to arc between the center conductor and outside braid. Now the end is prepped so the center Teflon insulation extends just beyond the braid and easily handles the full breakdown voltage of the cable without the arc on the end. Simple yet effective fix.

Thanks for the explanation, I suspected as such having read your earlier comments about the capcitor

 

[PsiDOC]

Morning all out in DX land.
Another update for you. A second homebrew GM has now been born and not made by me may I add.
The constructor, eddie (location unknown, but it's somewhere cold as he was testing it in temps of -21c!) used the as built dimensions I posted a couple of pages back and 72cm of Aircell7 for the stub (0.85 vf).
I am please to say it worked first time for him accross the FCC / Euro 40 channels with a flat SWR and contact made 25km away with a friend that was assisting the test.
If you'd like to follow it's progress then please have a read from this page on on TM1

On a personal note: Mine has been faultless - even in the seriously high winds of the last few weeks and I use it as my main antenna for 20 - 30 mhz now.
I have even built half sized version for 50 mhz that tunes from 48 - 57 mhz

This really is a brilliant little design and I am sure more can be got from this in terms of flexibility.

Psi

 

[camaro1]

want to try and make one of these homemade gainmaster's,,, the plans call for Westflex 103 coax for the matching stub

westflex 103 specs:

capacitance pf/m=78
velocity ratio=.85

lmr 400 specs:

capacitance pf/m=78.4
velocity= 85%

would lmr 400 work for the stub??

 

[camaro1]

Thanks to VKRULES for all the info on using rg-213 for the cap and stub and the dimensions,, made one tonight and turned out great.

 

[M0GVZ]

If you'd like to follow it's progress then please have a read from this page on on TM1


Psi

Psi your link doesn't work as they changed the URL for the forum. You need to change your link in your post to

Transmission1 View topic - Homebrewing a Sirio Gainmaster using RG58 and 2.5mm wire.

 

[camaro1]

tried out the homemade wire gainmaster today some more and my homemade walmart antenna launcher, got the wire gainmaster about 45-50' to the top in a pine tree and ran 100' of cheap rg8x coax to my hr2510 at 25watts, I had no problem making contacts all over today, even got out to robb from this site.

then I hooked some more coax to the 100' that is going to the wire in the tree so I could try them on an antenna switch back to back on my base radio,, the wire gainmaster was only 1/2 s-unit behind the real gainmaster on receive, the real gainmaster is about 20' higher and has better coax running to it.

so for only about $15 in coax and fittings(nothing fancy for coax/wire, just rg8x and rg-213) the wire gainmaster really works well,, I made a couple of them, this will be the antenna I use with my optima crate camping rig.

http://www.worldwidedx.com/installation-station-setup/166125-portable-camping-crate.html

 

[vkrules]

Glad yours worked out.Would love to see a direct side by side comparison with the real gainmaster, the copy should have less loss with the rg213 and handle more power. Ran mine side by side with a imax 2000 for a few weeks, Then pulled down the imax and sold it.With a 10 meter fishing pole it's my go to portable as well!.

 

[Needle Bender]

Glad yours worked out.Would love to see a direct side by side comparison with the real gainmaster, the copy should have less loss with the rg213 and handle more power. Ran mine side by side with a imax 2000 for a few weeks, Then pulled down the imax and sold it.With a 10 meter fishing pole it's my go to portable as well!.

I'm just wondering why no one has made one which centers on Ch.17 US CB band, that way it would be SWR balanced between 24.930MHz (12m) & 29.4MHz (10m) I don't know about you'ze guyz but I almost NEVER use anything above 28.910MHz.

After the NV4K - I think I'll take this one as a project, but I want mine to handle a pair of 4-1000A tubes.