Filter Pinout: P, E, B, G Explained

I few days ago I asked about the significance of the P, E, B, and G markings on my junkbox Toyo CM 455 kc filter (1969 vintage). PA3BCB -- in yet another example of the power of the International Brotherhood of Electronic Wizards --  was the first to provide the needed info.  And in another example of IBEW awesomeness,  KA0LDB noted that the markings are explained in the 1971 RSGB Handbook.   

P = Plate = filter input
B = B+     = mixer B+ plus if needed or input ground
G = Grid = filter output
E = Earth = Ground

I like the switched filter arrangement presented above (from the RSGB Handbook);  the 2.4 kc bandwidth is great for SSB, but a little tight for AM.  I might put in a DPDT switch in the circuit so as to be able to go back to the "broad as a barn door" selectivity provided by just the 455 kc IF cans.  


  

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Knack Pronunciation Guide: Kludge (as in Fudge)

A SolderSmoke listener (who will remain unnamed) recently corrected me on my pronunciation of an important Knack-related word:  Kludge.   I kludge as in fudge or judge.  He said it should be Kluge as in stooge.  I think we need a ruling her from our etymologist Steve Silverman.   Steve? 

I grew up listening to the 75 meter AM Northeast USA gang.  They said Kludge as in stooge, so I hope we stick with that.  

Wiki has an intereting (and seemingly endless) discussion on this topic: 
http://en.wikipedia.org/wiki/Kludge

Excerpts:


 'An ill-assorted collection of poorly-matching parts, forming a distressing whole' 

"There is a certain, indefinable, masochistic finesse that must go into true Kludge building. The professional can spot it instantly. The amateur may readily presume that "that's the way computers are." 

"The result of this history is a tangle. Many younger U.S. hackers pronounce the word as /klooj/ but spell it, incorrectly for its meaning and pronunciation, as 'kludge'. … British hackers mostly learned /kluhj/ orally, use it in a restricted negative sense and are at least consistent. European hackers have mostly learned the word from written American sources and tend to pronounce it /kluhj/ but use the wider American meaning! Some observers consider this mess appropriate in view of the word's meaning."

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Short Video of Mate for Mighty Midget

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A Filter for The Mighty Midget's Mate

The story of my 80/40 meter three tube (all 6U8) superhet receiver is recounted here:  http://www.gadgeteer.us/erart.htm

I've been playing with this RX on and off for many years now.  Somewhere along the line I picked up a 455 kHz filter for it (I couldn't find the 455 kc crystals that Lew McCoy used).  Yesterday I finally got around to putting the filter into the receiver.

There is almost no info on this filter on the internet.  Here are the details"
Toyo Communications Equipment Company Ltd.  CM FILTER
Type: 455 -- 2.4 -- C     Date:  8- 69

On the bottom, there are four terminals.  They are marked "P" "B" "E" and "G".   Does anyone know what these letters signify?  

 I experimented and it seemed like putting a 455 kc signal into P and B, and taking the output from E was the way to go.   I've left G floating. It works, and the improved selectivity is very evident.   But I'm operating with no specs on the filter, so I may have it in there upside down and backwards. And of course, I am operating with my usual disregard for impedance matching issues.

Here's how I've placed it in the circuit: 

Ideas, suggestions and even admonitions would be appreciated.

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Rich Arland's Global Adventures in Wireless Electronics

Rich Arland's SKN Station

Hi Bill:

I am writing to tell you what a GREAT book "Solder Smoke" is. I really enjoyed it and I am amazed at how similar our paths are regarding electronics, ham radio and our journeys around the world. 

Although I am 16 years older than you I, too, got my start in radio at an early age: about 10, after I got nailed by my dad's console SW/AM radio prior to a Cub Scout meeting one evening. I just had to figure out how I received a shock from that big old receiver, which led me to a life long pursuit of the elusive electron, an interesting 50 year career in ham radio, a 20 year career in the USAF (Tech Controller, AFSC: 307), and ultimately teaching vocational electronics in the State Correctional Institution at Dallas, Pa. 

During my AF career I spent almost 17 years overseas: two tours in Japan (KA2AA--this was prior to recip licensing as we had the Far East Amateur Radio League in the SOFA), a three year tour at Lajes Field, Terceira Island, the Azores (CT2BH--this was prior to the Azores receiving independence from Portugal in 1976), a five and a half year tour at RAF Mildenhall, UK (G5CSU), and a brief stint in W.Germany (DA2NE) while working with 10th SF Group at Bad Tolz and SOTFE in Patch Barracks. Had 18 months in the 3rd Mobil Comm Gp in Tinker AFB, OK, and a twilight tour at Langley AFB, VA. 

The three years in the Azores was from 1970-73....it was extremely difficult to obtain a ham license at that time and there were only 9 of us licensed in the entire archipelago, as I recall. I was attached to the 1936 Comm SQ, and all we had for comms to support theUS Forces Azores mission were three HF ISB shots: one to Andrews AFB, MD, one to Rota, Spain and the other to RAF Croughton, UK. During that three year period I REALLY learned about HF comm and propagation. I was on duty the day, in 1973, when "the ionosphere turned off"! WE had a SID of such magnitude that it blotted out everything, and I DO MEAN EVERYTHING! We were lucky to hear AFRTS on the hill by the MARS station! During that tour we also performed comm support for the US Navy's Sea Lab project on Sao Maria, which was part of the SOSUS system. Ultra cool stuff!!! On more than one occasion during a mid shift, the Comm SQ chief of maintenance, CT2BC, would snag me from tech control, and we'd go intoLajes Airways (right down the hall) and grab a Scope Control Level, point the two HUGE LPAs toward the states and work a little DX on 20M !! Definitely NOT QRP! All this under the guise of "quality control"! It pays to have friends in low places!

During my UK tour, we initially lived off-base at Bury St. Edmunds. I had a Ten-Tec PM-2B and a tuner which I loaded into a chain link fence behind our house. I quickly worked Collin Turner, G3VTT, and soon became a card carrying member of the G-QRP-Club (#622) in 1979. To celebrate my 34th birthday, my wife Pat (KB3MCT) and Jo Dobbs, wife of George Dobbs, G3RJV, put together a surprise party for me after a Saturday at the RSGB convention near Birmingham. George Burt, GM3OXX along with Ronny, GM3JJG, furnished the haggis....and the single malt....needless to say we did have fun; all 25 of us packed into RJV's home! 

Hey, sorry for being long winded. Our backgrounds and travels are uniquely intertwined. Thanks for writing "Solder Smoke". I am procuring a hard copy (I read it on my Kindle) for my wife, as your insight into the "why things work the way they do" are perfect for her to help her with obtaining her Extra. I only wish I had it when I was teaching my electronics classes in prison. It would have made my job easier, that is for sure. 

Stay well, and I hope we can meet one of these days. In the mean time, I have to pull my Meade ETX out of storage and start watching the sky, and finish building about four model rockets for an upcoming launch weekend here in North Georgia. 

Rich Arland, K7SZ
Dacula, GA

Author: "The ARRL's Low Power Communications, the Art and Science of QRP (all four editions)

ReplyReply All

Move...book editors

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The Raspberry e-Bay Multi-Mode Beacon of M0XPD

From: Paul Darlington 
Subject: Multi-mode QRSS beacon on the Raspberry Pi
To: "Bill Meara" 
Date: Sunday, January 20, 2013, 8:32 AM

Hi Bill

Inspired by recent comment on your SolderSmoke blog, I got myself a DDS module from eBay.

Today I lashed it up to my new Raspberry Pi and now have CW and Hellschreiber pumping out on 40m.

I hope others will forgive my greedy use of the spectrum in transmitting "m0xpd :- Raspberry Pi" in Hellschreiber.

The story is here: http://m0xpd.blogspot.co.uk/2013/01/multi-mode-beacon-on-rpi.html

73 de Paul, m0xpd

http://m0xpd.blogspot.co.uk/2013/01/multi-mode-beacon-on-rpi.html

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Drake 2B Filter Madness!

Wow, WB4HFN has ALL the details here: 

http://www.wb4hfn.com/DRAKE/DrakeArticles/HenryFilter01.htm

--------------------------------------------
Grayson:  Good to hear from you on this snowy morning in DC.   Wow, that's a bit of 2B history I hadn't heard of. Seems like a bit of overkill to me.  Maybe it was aimed at people who were unconvinced of the effectiveness of the LC filters?   Somehow, to me, it just doesn't seem right.  If you want more selectivity from a 2B, the thing to do is Q multiply using that socket on the back.  73  Bill 

--- On Wed, 1/23/13, Grayson Evans wrote:

From: Grayson Evans 
Subject: New info on the Drake 2B
To: "Bill Meara" 
Date: Wednesday, January 23, 2013, 1:43 PM

HI Bill, 

I was looking through the Dec. 1963 issue of 73 and came across an ad for a "New Mechanical Filter Modification Kit" for the 2A and 2B.  IT says "like magic the Drake becomes a truly superlative SSB receiver"  Model DMF-2 $29..  Says sold exclusively by Henry Radio, but does not say if they made it or not.  

Has a photo showing a module that plugs in (maybe a tube socket?) right behind the VFO.  Module has a mechanical filter (Collins I presume), two IF transformers and a tube (probably the tube it substitutes for).   I have been looking through a bunch of old CQ's and 73's, early 60's, and I only saw this one ad.  Probably a rare accessory, but how knows.

Thought you might be interested.  

Take care,

Grayson

TA2ZGE - Ankara, Turkey

KJ7UM

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Swamping or Q-Killing

Sounds like some new TV series on the Discover Channel, doesn't it? Actually it refers to efforts to stabilize oscillators by reducing the Q of components that may be helping to turn the amplifier into an oscillator.   A 300 ohm resistor across the primary of the output transformer on my most recent version of the JBOT amplifier recently solved my instability problem.  As part of an effort to understand how and why I came across a CQ magazine article by Doug DeMaw.  The relevant passage appears above.  

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An SSB kit from Spain

The ILER-20 and ILER-40 SSB transceiver kits of Javier Solans,
EA3GCY, look very interesting.

For more info: http://www.qsl.net/ea3gcy/


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DSB Audio -- Why Worry?

In a recent post I mentioned my concern about shaping the audio frequency response of my DSB transmitters.   This concern was sparked by an article in the May 1993 issue of "Electric Radio" magazine.   John Staples, W6BM,  had an article (the first in a three part series) entitled "Good Audio." The article (like most of ER) was focused on AM rigs and, it seems to me, contains a lot of technical wisdom.  Here is the part I found most relevant: 

"Good hamband AM audio is not the same as hi-fi audio. A broadcast-quality transmitter fed with a broadcast quality mike would sound flabby and under modulated. The highs would be lost in the narrow bandwidth of the receiver. The low frequency component would dominate the modulation power, but would be lost to the low frequency roll-off in the receiver.  What's left of the mid-range would sound weak, and the signal would lack punch.  Proper response shaping results in audio that sounds powerful, natural and undistorted." 

This seems to apply to DSB (suppressed carrier) audio just as well. 

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How to shape audio in simple DSB gear?

How should we handle the need for frequency response shaping in simple DSB transmitters?  If we don't roll off the lows and the highs, we risk wasting a lot of energy on RF that will be outside the passband of the SSB rigs on the other end.  This is especially worrisome if we use those cheap electret mic's that seem to have response curves from DC to daylight (well, maybe not that high, but you know what I mean). 

This is not a real concern with SSB rigs, because that crystal filter keeps our signals on the straight and narrow (!) but with DSB rigs, what is the best SIMPLE way to keep the audio between 300 and 2500 hz?    Is there an alternative to the 741 op amp configured as an audio bandpass filter?  

73  Bill N2CQROur book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Il Fido -- A Simple Receiver from Italy

As part of a refresher course in Italian, I am reading a bunch of old radio magazines from Italy sent to me by Stephen.   There are some really wonderful projects in these magazines and I feel compelled to share them with the SolderSmoke community.  No full translations yet, but perhaps that would provide a good language learning opportunity.  For now, just schematics and drawings (aren't they beautiful?).   

This one is a simple crystal receiver with one stage of AF amplification.  It covers the AM broadcast band, the HF bands, and (apparently) VHF using a switch and three different coil/capacitor combinations.  You could make it a lot simpler by just building it for one band.  Looks to me like a nice rig for an Altoid tin. 

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