Coil construction for link coupled grid input?

[KC9LKE]

After some reading and research I decided to get a better understanding of a link coupled, grid input circuit. I wound coils for 80 & 10 to be put in parallel with a 100pf variable. The load is a “grid mockup” consisting of a 5k & 32pf in parallel.

Very interesting. I can see how C and L affect the skirts, also the affects of turn’s ratio, form factor, etc. However I did not see much difference with the placement of the link coil with regards to the input coil.

I have read articles that suggest winding the link coil at the hot end, cold end, and middle, but without explanation.

I should add that the coils are wound on a form, they are not the air-core w/ swinging link type.

#1 Any ideas on how the link coil placement relative to the output coil affects the circuit?

#2 Also I plan to build a “turret” assembly, two coils for each band ‘link and output’, and use two separate wafer switches to select the coils. Should I short the unused coils or just leave them open. I plan to place the coils at least one diameter away from each other.

I might try the all bands in-one form, but like individual coils for know.


Thanks again.
Ted / KC9LKE

[KL7OF]

editors and Engineers handbook ....I think it is the 15th edition.... has an "all band grid tuning unit that is working well for me

[k4kyv]

The link should always be placed around the "coldest" part of the coil.  With a balanced tank circuit, this should be near the middle of the coil. With single-ended, unbalanced, it should be at the end of the coil that is grounded.

Placing the link at a coldest spot reduces the capacitive effect of the link on the resonance of the tuned circuit, and also  reduces the transfer of harmonic energy between the the coil and the link.

If there is any  doubt, the easiest way to  find the cold spot of the coil is to use a neon lamp while the tuned circuit is energised.  Move the lamp up and down the coil.  It should go out at the cold spot, or at least show minimum glow.

[KC9LKE]

Thanks Steve and Don for the suggestion and explanation.

I enjoy building but feel I owe it to myself to read the book,
 work through the calculations, build the circuit, and learn from it.

Thanks again for the suggestion and explanation.

Steve: I looked on the web for "Editors and Engineers handbook” and didn’t find anything, any leads?

Ted / KC9LKE

[WD5JKO]

Steve: I looked on the web for "Editors and Engineers handbook” and didn’t find anything, any leads?

The 1959 addition is here:
http://www.amforever.com/

Jim
WD5JKO

[KC2ZFA]

design charts, etc., in the October 1955 RCA Ham Tips available
here: http://n4trb.com/AmateurRadio/RCA_Ham_Tips/rca_ham_tips.htm

[w3jn]

Steve: I looked on the web for "Editors and Engineers handbook” and didn’t find anything, any leads?

Ted / KC9LKE

AKA "Radio Handbook" AKA "West Coast handbook"

Its formal title is "Radio Handbook" by Editors and Engineers.  Later issues were edited by Bill Orr.

[KC9LKE]

OK the Don Orr handbook. Yes I need to download it sounds interesting.

Thanks agian
Ted

[Steve - WB3HUZ]

Don't confuse the Don Orr ones with the earlier ones edited by Frank Jones and company. The earlier ones were better IMO.

[KB2WIG]

The previously mentioned books, along with a whole wagonload of gud stuff is to be found here......


 http://www.pmillett.com/tecnical_books_online.htm

[Ralph W3GL]

    "Don" Orr? Who he?

[KM1H]

Thats his brother, the family name was Orratero before they got kicked out of Brooklyn by Don Corleone

[KB2WIG]

       "   "Don" Orr? Who he?   "

The Godfather of handbooks.


klc