Excellent video as always Charlie, I ordered a few AD8307's a while back but haven't really done much with them. They should give you 25mV out for every dB in. I do like the idea of the little stand alone filter checker, that could come in very handy... 73, M1CEM.

@CharlieMorrisZL2CTM

6 жыл бұрын

Cheers Brian. I will add filter analyzer to the list of things I want to build. My approach will be simple as always. I'm also thinking that it should be possible to feed the filter output straight into the arduino, as I've done for the antenna analyzer, and do the log maths there. We'll see. All good fun!

Very instructional video, many thanks, I've discovered your channel recently (sorry for being late..) and I've started following your projects, not much (free) time now for hobbying so your videos help me to compensate this 😃 . One Q: what's the material type of the impedance transformers (sorry if I've missed it)? I was wondering also, whether the near-spaced copper tracks on the PCB have any noticeable influence (e.g. due to parasitic capacitances, etc) on the filter's response, but I guess for HF it shouldn't be a big issue (?), you indeed have removed copper tracks to increase spacing and hence reduce unwanted couplings, etc, 73

Hey Charlie... You know what happens when someone sneaks into your Google doc spreadsheet and lowers the capacitance on your pass filter?

Great video Charlie. Hey, did you ever see the January 1990 (pg.21) article titled "A tester for F, Q and R", it was also on page 192 of Doug DeMaw's "W1FB's Design Notebook" published later that same year? It is a refinement on some disparate circuits that Hayward presented in his Crystal Ladder design article. I have thought about building one eventually myself. 73...

@CharlieMorrisZL2CTM

3 жыл бұрын

I don't think I did. I'll have to look into that. The latest Cohn filter worked very well. The SSB receiver is sounding great (to me al least!).

So, is there a source for higher Q crystals? A lot of stuff from China is sub-standard but in some cases, improving.

Charlie, I'm not clear what your filter and I might add what Wes Hayward's filters were going to be used for. I have only seen CW filters and SSB filters used in intermediate frequency stages of a superhet receiver. If that is the case the IF frequencies commonly are 455 kc and 9 mhz for a double conversion receiver. Respectfully what use is your 7 mhz filter?? Are you designing a receiver with a 7 mhz if filter?? I just don't get this. I never have. I've always been confused with Wes Haywards article.

@CharlieMorrisZL2CTM

2 жыл бұрын

Hi Douglas. I suspect you have the answer to this now. Correct?

11 dB does seem high! But then I measured 6 dB through my 4-pole filter. I imagine more crystals will lead to more insertion loss. I wasn't measuring with any impedance transformation, so I'd assume the insertion loss would decrease if I had a better impedance match. Do you have an idea what sort of losses you can expect on your transformers? If you look up "Scalar Network Analyzer" by rheslip20 here on youtube, he's done a nice job with an AD8307 and AD9850 along with a basic preamp. I'm thinking of doing that as a project once I finish my current radio (finishing up the IF stages and crystal filter then moving onto the RF power amp).

@CharlieMorrisZL2CTM

6 жыл бұрын

No I don't sorry, but it wont be lossless! I suspect too that the Q of my cheap crystals wasn't that high so overall with more crystals the loss is higher. I think a homebrew scalar network analyzer would be useful to speed things up. Another project to add to the list.