Just Sharing This AV-Comm Polariser + Zinwell lnbf

[Trust]

John , if you have enough tubes , you can do that , but ......
Cardiff did send me a raw AV-COMM barrel to machine it in the proper way , did that yesterday at my employers lathe .
This morning I tested it at a 1.2 m Echostar Offset dish pointed at 5 west TP 4115 .
With the AV barrel managed to get 10.7 dB .
My barrel 60 mm inside with 48 mm between the second steps ( D2 ), showed 10.1 dB
Put some 0.5 mm thin plates between step 1 and 2 to become a D2 of 47 mm , showed 10.4 dB , some increase !
Fitting the step plates with screws allow you to tune the barrel .
So I decided to make new steps for a D2 of 46 mm , no good idea , signal drops .
Than I machined my second tube to a inner size of 63 mm and made new step plates for a D2 of 48 mm , about the same dimentions as from the AV barrel .
The test will be made when I'm back from the dentist

 

[John]

John , if you have enough tubes , you can do that , but ......
Cardiff did send me a raw AV-COMM barrel to machine it in the proper way , did that yesterday at my employers lathe .
This morning I tested it at a 1.2 m Echostar Offset dish pointed at 5 west TP 4115 .
With the AV barrel managed to get 10.7 dB .
My barrel 60 mm inside with 48 mm between the second steps ( D2 ), showed 10.1 dB
Put some 0.5 mm thin plates between step 1 and 2 to become a D2 of 47 mm , showed 10.4 dB , some increase !
Fitting the step plates with screws allow you to tune the barrel .
So I decided to make new steps for a D2 of 46 mm , no good idea , signal drops .
Than I machined my second tube to a inner size of 63 mm and made new step plates for a D2 of 48 mm , about the same dimentions as from the AV barrel .
The test will be made when I'm back from the dentist

View attachment 99461 View attachment 99460

Ohhh Dentist !!
Thanks for the test info Wim, very useful to know

 

[Trust]

Its hard to compare the barrels by the cloudy weather , tomorrow I'll catch me a second 1.2 m Echostar that carries the AV-COMM constantly .
Have to make a C- lnb holder for that one too .
A short test with my 63 mm barrel was looking goed , almost the same performent as the AV .
Also finished a part of Cardiffs wishes .

 

[John]

... If it's not too late Wim, can you do a test on a freq at the bottom end and top end of the band

 

[John]

.... Just a measurement comparison Wim from an aprox 10 yr old AV-Comm barrel .... accuracy to nearest half a mm / or quality of cheap measuring tool.
Not a lot of difference if any, over the years.

 

[Trust]

... If it's not too late Wim, can you do a test on a freq at the bottom end and top end of the band

No much chance at 5 west with a 1.2 m dish overhere to catch bottum and top .
Spend most of the day collecting a second 1.2 Echostar and make a stand and C lnb holder .
Tomorrow I will turn them to another sat , 20 E ??

 

[John]

Just wondering this Wim ....
when you were doing the comparisons between the pucka AV-Comm and the home brew barrel did you put the signal through an analyser display to evaluate the efficiency of the home brew re: X-Pol, did it completely go down to noise floor without any trace of the opposite polarity when looking at a RHC signal or visa-versa ?.... could this have been a reason perhaps that your 1st tests were a fraction down on C/N ?.
My AV-Comm barrels manage this ok but i think it's another aspect of home brewing that has to be took into consideration to get 100% performance.
I like your 1.2 test antenna Wim, i think i,m going to use my spare 1.2 Precision at ground level to do the testing on my home brew barrel.

 

[Trust]

No John , nothing scientific , just watched the signal meter at my F16 .

 

[pride21]

hi can somebody let me know the length of the second step please.

 

[John]

hi can somebody let me know the length of the second step please.

These are the measurements took to the nearest 1/2 mm from an ADL polariser barrel and also an AV-Comm barrel, they were virtually identical. Precise measurement is a bit difficult as the sand casting of the originals are not exactly finished with defined edges.
Good luck with it, keep us up to date with your progress.

 

[pride21]

thank you for that john.

 

[John]

thank you for that john.

Meant also to say that the "Front" of the barrel is the 38mm / 66mm measurement

 

[blademedia]

Anyone considered casting this, its very easy to do and cheap if you make your own furnace
http://www.flamingfurnace.com/p/sand-casting-terminology.html

 

[John]

Anyone considered casting this, its very easy to do and cheap if you make your own furnace
Foundry & Sand Casting Terminology ~ Metal casting projects

Well, we nearly have all the parts now .... Vipersan has the barrel mould, we have the furnace details, we need a stack of old pop cans and away we go.
Who's up for a new project venture to keep them happy for a while ?.
Btw BM .... you done that welding yet ?. ;)

 

[blademedia]

Btw BM .... you done that welding yet ?. ;)

Not yet John, chain ring nearly finished, just been out planning my next move, need to cut and weld this now, middle parts easy

Who's up for a new project venture to keep them happy for a while ?.

Yes me when ive finished my other projects, nice winter project melting ally, if all fails at least will be warm doing it

 

[John]

Not yet John, chain ring nearly finished, just been out planning my next move, need to cut and weld this now, middle parts easy
View attachment 99618




Yes me when ive finished my other projects, nice winter project melting ally, if all fails at least will be warm doing it

... lol, i was going to put your name forward but thought you had enough on your plate at the moment

 

[blademedia]

... lol, i was going to put your name forward but thought you had enough on your plate at the moment

Never done any casting before, but used to have furnace for melting ally to ingots, doesn't look hard to do, will have a go at some point, I have plenty to do atm,

One word of advice make sure you use face mask welding gloves, and don't get any water in melted ally it will explode and fly all over, I learnt the hard way was lucky not to be blinded

 

[pride21]

thanks john

 

[John]

... As a bit of a departure from the normal 3.4GHz-4.2GHz barrels, i have four of these already, i thought i would knock something up to try on my extended Cband 4.5GHz to 4.8GHz lnb.
I have tried it with the standard frequency size barrel and know what it will do so will be interesting to see if it can be improved apon by going a fraction smaller.
Just using basic tools, cos thats all i has ive knocked up this bit of a cheapo thing using simple ali flat bar and some sticky back ali foil tape and a bit of 60.5 ID steel tube with 1mm wall.
The step gap can be altered if required by shimming to fine tune if required.
No pain, no gain ...worth a try
Pic shows the home brew aside the normal AV-Comm barrel

 

[scopus]

The last time I did any ali casting was at school, Made a tootbrush holder....