Hi Tom, I forgot to mention earlier that I have a partial schematic of an old Hughes amplifier, which includes RF feedback around the last two stages, posted on my website. http://wc6w.50webs.com/wc6
Hi Marv! Now THAT'S the kind of info I've been looking for, OM. OK on using the 'J' tube versions and the TRW class A chips. I imagine the J's are harder to find used. I went to a site that has a CA5
Marv: Looking at the schematic of the Hughes 10 kW amplifier proved to me to most beneficial in terms of neat things to do, try, learn from! Thanks for posting the link for us all. - Jim WB6BLD _____
Tom, Also look at the schematics of the Collins KWM2 or 32S1 and the Collins KWS1. They all use negative feedback and show real values. The collins uses what they call a "feedback neutralization" cap
Hi Tom, That '5106 is probably for Cable TV use and likely cuts off around 40 MHz (on the low end!). If I recall correctly, some of the general purpose units that go down to a MHz use numbers from CA
CA2820 and 2830 are good ones, 0.5-1W capability and only a couple of power line decoupling caps needed. Motorola equilvalents are MHW590 and 592 - these replaced the TRW parts after Mot bought TRW.
That's more valuable info, Marv - Tnx again! A few follow up questions: If I tap off the FT-1000D 10mW low level point, can I run a long ~ 20' coax cable to the amplifier CA2XX module's input, or wil
Hi Tom, You do have a spectrum analyzer in your shack! Your receiver. Modulate the transmitter with 2 tones and tune across with your cw filter on another receiver. Note the level of one of the tones
Better yet, if the two tones are only a hundred Hertz or so apart, you can take the audio output of the SSB receiver and put it into the sound card of your computer and do an FFT. You can use a numbe
Hi Gary, Tnx for the IMD measurement info. Sounds easy enough. Actually I've been doing a similar thing, but using a recorded voice to play thru the rig and measure the bandwidth and levels. I will m
The IMD data for the 4CX350FJ looks quite attractive ! -45 db 3rd order products and -50 db 5th order products. Without negative feedback. http://www.g8wrb.org/data/Eimac/4CX350FJ.pdf The price of 4C
Amen, Gary. For most of 'em, the s in S-meter stands for sucky. Step-attenuators are typically way more truthful. Richard L. Measures, AG6K, 805.386.3734. www.somis.org ______________________________
In theory, you can measure transmitter IMD at the receiver output, but in the real world this also results in influences of the receiver in-band IMD characteristics. Only few HF receivers are specifi
In theory and practice. This is how most "DSP IF" receivers work. The last IF is 10 or 12kHz from a product detector "mixer" and then to a DSP board which in this case is a PC. Naturally you can't al
Good point Karl-arne. Because of this it is important to keep the signal level relatively low into the receiver. 40 over S9 is probably pushing it on input level. An easy way to tell about receiver I
In principle I agree, and it works as advertised when you pick off the "IF" at a sufficiently early point in the receiver so the IMD performance of the stages before the audio output does not enter t
Marv, Just as a note on your Hughes sample amplifier URL below.... I see no negative DC bias on either the 4CX-250 nor the 4X10. Strange that it's not there. Bias is OK on the 6146. Would appropriate
Tom, As a follow up to specing IM products to PEP. Some of the same tricks are used by manufacturers when specing 3rd order intercept points for VHF/UHF pre amps. Some will spec them with reference t
Don't take that for granted! Depending on the levels, good generators with a good combiner should be ok, but I've seen people assume that and then spend time chasing problems that were in the source
Neither the 4CX250 nor the 4CX10000 have any DC grid returns, which would lead to unstable DC operating points to say the least... To me this looks like drawing errors, maybe in combination with sche