[Hammarlund] NOISY FRONT END TUBES

[Carl]

Re: [Hammarlund] NOISY FRONT END TUBESOne important thing to rmember when characterizing a tube is that it is done at DC. The transconductance can give you a fair idea of RF performance but there is nothing to tell you at what frequency NF performance will begin to suffer.

The 6BZ6 and 6GM6 are classic examples. In a NC-270 the receiver is almost deaf on 6M in stock condition wheras it is very much alive with the 6GM6. IMO the 6BZ6 has reached its max around 20 MHz.

Another tube that warrants inspection is the 6JK6/6JL6.

I picked up a HP 8970A NF Figure Meter a few years ago and have been using it mainly for VHF thru microwave SS work. However as time permits I move it over to the boatanchor bench to tweak and measure gain and NF on some new idea Im trying out or receiver that I have modified and want to check the system NF before buttoning up and putting it on line.

I started a new  forum a few days ago which already has close to 90 members. It will be stressing performance, mods, homebrew, testing and servicing procedures, etc across all brands of tube equipment. Check it out.

QTHnet  rules do not permit me mentioning the host name so if you dont figure the link out please email me.

****://groups.*****.com/group/glowbugradio/

Your tube results will be most welcome in the Files section.

Carl
KM1H