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"Ah, Grasshopper, It is good you asked this question." ( If you'll forgive a KungFu paraphrase.) All the equations governing the time and frequency behavior of filters are well defined. The

Hi! I am puzzled about the fact that using 2 cascaded, overlapping filters results in less ringing than a single CW filter with same resulting bandwidth. Have you experienced that or is it a guess? I

I recently bought an Icom 705 and have been stunned by the performance of twin tunable pass band filters. I want to duplicate that using analog filters. As it happens, 5 MHz HC-49/S crystals are

That's cruel ;-)

In Paris found a French made Vibroplex circa 1950s..1960 NIB, paid €5! Jon

I bought an Icopm 705 a few weeks ago and it has me very eager to get re-licensed. I was looking for a Vibroplex Code Warrior Jr. but couldn't find one in stock, so I waded through the ebay listings

Hi all QRP Labs kits are heavily dependent on the Si5351A from SiLabs. Sadly this chip is a victim of the ongoing global semiconductor shortage, and perhaps also the acquisition by SkyLabs, of parts

My interest in codes started when I was in high school, even wrote an article for the local paper. Your article was awesome, very clear descriptions, many useful photos and insights. Thank you!

Fascinating article-and very fine photos, too. I couldn't stop reading. Dave

Jon, Many thanks, that is very cool! I was enthralled by crypto in my teens. The central repository librarians for the state of Arkansas got me a used copy of "Secret and Urgent" which I coveted

Hello all: My IEEE Spectrum article about a 1963 cipher machine and a huge espionage case Rubicon just went

I'm looking at this as an EM support function. First responders depend on radios. And we have all seen many trivial repairs that required significant diagnostic tools but took no time to execute.

Hi Reg, That's quite a list. For Field day I figured a dmm and an antenna analyzer was about all I would need. If I needed more test gear to get my setup going for FD I'd turn to socializing.

I'm assembling the following suite of test kit just to see what it can do for radio design work. After evaluating the performance relative to my mid 90's HP & Tek kit, I plan to use this kit to do

I don¡¯t understand why, but feedthru caps have gone way up.

Somehow it didn't register they were $1 each, not $4. I just ordered 40. Reg

Dave, Thank you! That's exactly what I want. Don't like the price though. However, it's less than what I've found in my searches which were not what I wanted anyway. NOS HV was all I found in my

Maybe something like this: https://www.mpja.com/Pack-of-4-Capacitor-Feedthru-1000pF/productinfo/36701+CF/

I have a bunch of RF eval boards from China which I want to connectorize in shielded enclosures. I don't want to spend $20 packaging a $8-15 board. I make the enclosures from scrap 28 gauge

I just received my copy of the July/August issue of QEX and can now take a look at the article. DaveD