Hi Paul, K1FO has done the work already. Why not use his dimensions for the
stripline?
Is there a space problem?
Adding 3/8" to the short end of the line will have very little effect on
the resonant frequency. The long end controls that, hence the question above.
73,
Gerald K5GW
In a message dated 1/5/2012 9:51:10 A.M. Central Standard Time,
kg7hf@comcast.net writes:
Hi group,
I have a homebrew 70 cm stripline amplifier built around the 3cx400A7
tube. As everyone know's, it's getting rare and expensive. I was thinking
that it would be really easy to change over to a 3cx800A7 or 3cpx800A7 tube
since it uses the same socket (I have a few sitting around), and comparing
the datasheets, they are electrically very close. Besides the obvious like
size and heater voltage, there are slight differences in cin and ck, but
I'm not sure how that will effect it.
Because the tube anode cooler is physically bigger, I would have to make a
new stripline with an extra 3/8 inch on the end. My question is two
fold. 1. How does one calculate the actual length of the stripline in the
first place, and 2, more of immediate concern is would that extra 3/8" make
any
difference? My "gut" feeling is it won't, but I have no basis for that.
Here is a picture of the stripline out of the rfdeck:
http://a4.sphotos.ak.fbcdn.net/hphotos-ak-ash4/388232_2684319340428_10296933
54_32301613_317232212_n.jpg
My current stripline is 8.625" and I would extend it to be 9.0". I looked
at K1FO's single 3cx800A7 design and his stripline is 9.6875 and the same
width of 3.5". I also looked at his 2x3cx800A7 design and that stripline
is 9.0", the same as mine would be.
Here is a picture of the whole amplifier project:
http://a5.sphotos.ak.fbcdn.net/hphotos-ak-ash4/247265_1908478664896_10296933
54_31782436_481699_n.jpg
Just to head anyone off at the pass. I am doing this for two main goals.
1. So that I have a replacement tube, and 2. more power and more
headroom for JT65. (I way more voltage and current than the 3cx400 could ever
want, plenty to supply two 3cxp800's). I thought this would be an easy
stepping stone for now.
Thanks and 73,
Paul, kg7hf.
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|