Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

donate to eham
   Home   Help Search  
Pages: [1] 2 Next   Go Down
  Print  
Author Topic: SimpleX Super Receiver (1959 ARRL Handbook)  (Read 1996 times)
AE7TE
Member

Posts: 53




Ignore
« on: November 05, 2017, 10:10:28 AM »

I've been doing a lot of rambling about tube transmitters lately, but I feel like a receiver would be a better place to start in my desire for an all-tube station. I recently got a 1959 Radio Amateur's Handbook and it has a few receiver projects in there. There's a 6U8A regen that seems lackluster for me, as I've built simple regens before. The next one, the SimpleX Super", uses a 5Y3GT, 6U8A oscillator and mixer, 6U8A second detector and BFO, and 6CG7 first and second audio. It covers 80 and 40 meters with a 1700KC intermediate frequency and a crystal filter.

I don't have a lot of interest in 80 meters, but I would like to make something similar that can receive 40, 30, and 20 using a 1700 KC IF. I'd also like to add in an IF amplifier. A 6BJ6 or something similar, with a manual gain control. The biggest problem will be switching bands.

To do this, I could have a single, parallel tank per band on the input. The band switch would ground the tank for whichever band I've selected. The oscillator coils would be selected in the same way. Once I had the detector, IF amplifier, and audio sections, making the RF front end would be simpler. I also could make the oscillator and preselector coils on powdered iron toroids.

Another problem I may run into would be fabricating the IF transformers, which would require a 160 uH inductor and 47 pF capacitor. If I could get them to transfer the signal, I might have something here.

The other thing is, I'm not sure whether I want to go through all of this trouble changing the circuit, or just make the thing as-is and deal with 80 and 40 reception.

Ed AE7TE
Logged
VE7DQ
Member

Posts: 220




Ignore
« Reply #1 on: November 05, 2017, 04:22:19 PM »

I built one of these out of the 1961 handbook.  In the process of improving the radio I added an IF stage using a 6BA6 and changed the grid-leak detector to a product detector using a 6BA7 pentagrid converter.  To aid stability, an 0A2 supplies power to the oscillator circuits.  Of course, being young and ignorant, I never documented the changes!

While the performance was satisfactory back in the mid-60s, I found it lacking in stability and I never could get the thing to remain on frequency very well.  There may be some issue with the Hammond power transformer I used (which runs very hot) although the specs were correct as per the parts list.

I still have the radio, 1961 handbook and the RCA tube manual from that exercise.   Grin

There are so many better circuits out there for receivers; if I were to do a tube station again, and I've considered it, I would go for something more elaborate.  Maybe a single-band receiver (80m perhaps) with a bandswitched crystal-controlled converter for the frequencies of interest in front of it. 
Logged
WB6BYU
Member

Posts: 17046




Ignore
« Reply #2 on: November 05, 2017, 05:58:56 PM »

Are you wanting to use vintage parts?  To have vintage performance, or something better?

The oscillator coils from AM BC receivers should work well for 1700 kc tuned circuits.  You aren't
worried about having as wide of a tuning range, so you can use smaller coils with more capacitance
(which may improve your oscillator stability, too.)   Coils from transistor radios are still common,
and if you aren't worried about having to document the receiver for others to duplicate it you can
use whatever parts you can scavenge without worrying about specifying a source.

In fact, it isn't uncommon for folks to unwind the transistor IF cans and rewind them for specific
purposes.

For more modern performance, I'd suggest getting some standard frequency crystals in the HF range
and making your own crystal filters, at least for SSB and CW.  (I don't know how they would work on
AM bandwidths.)  That puts the IF up higher in frequency, so your oscillators can run at lower
frequencies and hopefully be more stable.  It also makes winding your own IF transformers easier, or
you can use standard 10.7 Mc cans with additional shunt capacitance across the windings

Bandswitching used to be a separate coil and trim cap for each band, so required 3 or 4 switch wafers.
If you only want to cover 40 / 30 / 20m you probably can get by with a single coil (and secondary
windings) and just switch the capacitor across it.  That's still at least two sets of contacts, for RF input
and oscillator, of course.

1700 kc would give you a spur at 10.2 Mc, but at least it is out of band.
Logged
N2EY
Member

Posts: 4436




Ignore
« Reply #3 on: November 05, 2017, 06:40:12 PM »

Ed,

There are probably easier ways to do what you want to do.

---

The SimpleX Super and similar receivers (there were a lot of them) were designed to maximize what could be done with a few tubes and low-cost parts.

The design is what is known as "band imaging" - you get two bands by simply retuning the input circuit. This is both good and bad, because if there is a strong signal on, say, 7100, you may hear it on 3700 if the front-end doesn't have sufficient selectivity.

Note that the same oscillator range (5.2 to 5.7 MHz) is used for both bands. This maximizes stability and minimizes cost. (Believe it or not, the reason so many projects of that era used Miniductor was because, back then, it was cheaper than wire and a good coil form!)

The higher you go in frequency, the harder it is to build a truly stable tunable oscillator. Bandswitching complicates the issue too.

73 de Jim, N2EY
 

Logged
N2DTS
Member

Posts: 725




Ignore
« Reply #4 on: November 06, 2017, 05:31:59 AM »

I have built a couple of homebrew receivers and would go with a simple single conversion superhet with a 455 KHz IF.
You can get good filters for 455 KHz.


Has 2 filters, an S meter, a digital readout and works on 80 and 40 meters but could do 20 as well.

When I started, I wanted a home brew RX to match all the transmitters just so I could say it was an all home brew station.
I did not want a regen, they can be very touchy, and many of the old designs used parts that would be hard to get now, plus I wanted a good filter in the IF.
I thought about the all American 5 type RX, tuned input into a mixer, out of the mixer into a filter, a few stages of 455 KHz IF amp, a detector and agc.
I added the S meter circuit and the digital display (freq counter with a 455 KHz offset) and a 455 KHz xtal osc as a bfo with screen voltage control for a bfo level.
I built it to be an AM receiver and it works fantastic for that, so good in fact I sold all the boat anchors and just use the home brew.
Its very quiet, and pulls out the weak signals even better then my Anan 100b or icom 7300.
No RF amp is needed if used with the TX antenna (a full size antenna), the input is a link coupled tuned circuit using B+W coil stock and a 365pf cap, very high Q. I have no images or birdies or anything like that.
The 6C4 LO runs on 100 volts, the rest of the RX runs at 150 volts.

Making a good receiver is a lot easier then you think.
Logged
KB1GMX
Member

Posts: 1496




Ignore
« Reply #5 on: November 06, 2017, 02:23:17 PM »

I"ve built that radio with one mod.  The IF was 1.824mhz (common crystal).  For 75M use it was very good for AM and SSB
but a bit wide for CW.

For 40M it needs more gain and better front end selectivity as image were a problem.   At 20 a tuned RF
(more like two double tuned section) is both for sensitivity and image rejection.

My solution was good 80/75M coverage and an external two tube down converter for 40, 20 and even 10M.
That was the approach usually taken back then.

Good quality components and layout (keep cooling in mind)  makes for decent stability.  I found a VR tube
helped with VfO and BFO stability.  With that mod listening to SSB was fairly easy.


Images are mor an issue with that radio.   Gain is fairly high ass the second detector is regenerative
so little gain is needed ahead of it.

Allison
Logged
AE7TE
Member

Posts: 53




Ignore
« Reply #6 on: November 06, 2017, 09:53:14 PM »

Quote
There are so many better circuits out there for receivers; if I were to do a tube station again, and I've considered it, I would go for something more elaborate.  Maybe a single-band receiver (80m perhaps) with a bandswitched crystal-controlled converter for the frequencies of interest in front of it.

That's another thing I thought - make this rig, with 500 KHz of tuning range, then arrange a downconverter to get more HF bands. I'm interested in 30, 20, and 15 if I can wrangle it, but mixing the frequencies that are multiples of 7 MHz might be tough. Might be better to mix 20 and 15 meters down to 3.5 MHz instead. There's also 17 meters which I might have to grasp. Not sure yet.

Quote
Are you wanting to use vintage parts?  To have vintage performance, or something better?

I'm wanting to use tubes. I'm not against using some contemporary parts, such as plastic polyvaricons or toroidal inductors. It's my project and I'll take the liberties where I feel comfortable. The tubes are the important part. I'll likely be winding my own IF coils unless I find some RF chokes that will fit the bill. I'm not quite comfortable with crystal filters yet. This is doubly so when crystal filters have terminal impedances of a few hundred ohms while tubes like impedances of a few tends of thousands of ohms. I can also see myself trying to repurpose 10.7 MHz parts but I'd have to put some thought into it. I also have 455 KHz ceramic filters. If I could isolate them via transformers, I could use them. That would also be the way to work into crystal filters should I try to go that route.

Quote
There are probably easier ways to do what you want to do.

Story of my life. I have an IC-718 and a K1. There are definitely easier ways to do things than the way I make them, but for me it's mostly the fun of doing it. I've done the whole regen thing. I'm sure it would work. I'm also sure I'd get more enjoyment out of a radio with higher performance. I built a two-stage TRF once and it was nice. However, a superhet is like a TRF. I'd much rather get some practical experience building one of these. My last attempt at making a superhet ended in disappointment. It would make me very happy to succeed.

Quote
The higher you go in frequency, the harder it is to build a truly stable tunable oscillator. Bandswitching complicates the issue too.

Yes. When I read the 50s and 60s manuals on how to build this or that, it seems clear that the best option would be to make a stable, clean oscillator at 1750 KHz, then double it two or three times to get the frequency I want. Then I realize I have access to digital synthesis and the rest is moot. However, it's something I want to achieve, so building a stable tube oscillator will be part of my radio education.

Quote
The SimpleX Super and similar receivers (there were a lot of them) were designed to maximize what could be done with a few tubes and low-cost parts.

That's always a factor - if it weren't, I'd buy a custom wound transformer and make a 25-tube behemoth that takes two stout men to move and dims the lights when I turn it on. I like the idea of getting decent performance with only three tubes (albeit double-tubes). I'm also thinking of sticking a fourth tube in there as an IF amplifier, to get some extra gain and selectivitah. If I change the output tube from 6CG7 to 12AT7 or somesuch, I might be able to afford the extra power in my little transformer to put in a pentode like 6BA6 or something. I have a 6EH7 I've been dying to use as an IF amplifier. Their transconductance is through the roof....

Should I really want to go "old school", I'd buy a mechanical filter and use that. Too bad they're $$$$$$$$.

Quote
No RF amp is needed if used with the TX antenna (a full size antenna), the input is a link coupled tuned circuit using B+W coil stock and a 365pf cap, very high Q. I have no images or birdies or anything like that.

That's another thing I'm hoping...that the construction of an analog receiver without a bunch of digital circuitry might be quieter. I also know that high Q in a parallel tuned circuit also normally means a lower inductance value with corresponding high capacitance. With the right tuning capacitor, it could be enough to provide superior image rejection. It's a given that a full size antenna would provide more signal than sixteen feet of speaker wire stretched out wherever I can get it.

Quote
For 40M it needs more gain and better front end selectivity as image were a problem.   At 20 a tuned RF
(more like two double tuned section) is both for sensitivity and image rejection.

Yeah. My intent would be to use high Q components (maybe thicker-gauge wire on the input coil and a higher-grade capacitor). Maybe a receiving converter would provide extra image rejection. I'm thinking a VR tube as well. I have some of the 105-volt tubes. I'm really considering the extra 6EH7 as an IF amp to provide extra selection and gain. Still not sure if I want a manual gain control or not.

Ed AE7TE
Logged
N2DTS
Member

Posts: 725




Ignore
« Reply #7 on: November 07, 2017, 10:30:55 AM »

My receiver with no rf amp picks up strong stations with the dummy load as an antenna.
For diagrams look here:

https://n2dts.smugmug.com/Ham-radio/i-mn5BP3q/A

Page forward for each section.

The RX is very stable, very quiet, very high fidelity.

Its easy to build, the LO takes no special parts or tricky coils, and will work down to 10 volts on the plate of the 6C4!
Logged
KM1H
Member

Posts: 2458




Ignore
« Reply #8 on: November 08, 2017, 08:49:52 AM »

A couple of things come to mind:

1. With no RF stage and a 455 kHz IF image rejection will be poor even on 20M.

2 With a Vackar VFO stability will be better than most other circuits but you still have to pay attention to the details including mechanical stability.

3. Id suggest a Pullen mixer as the best for a tube circuit as well as simple with either a 6J6 or 12AT7. If you want to get fancy use the 6ES8 dual triode and apply AGC.

4. Follow that with the xtal or ceramic filter and most any generic pentode IF amp as the NF is already well below atmospherics, even 10M.

5. Consider a 2 stage tuneable passive preselector which will improve image rejection as well as loading effects on any mixer and oscillator. The 6BE6 is particularly prone to this and the 6BA7 is not that easy to get right; just look at the rather deaf 75A3/75A4 and SX-115 compared to the hot NC-300/303.
If you wind up with too much loss use a 6BZ6 or 6GM6 as the IF amp to sufficiently recover the NF.

6. You can cascade IF cans on the input and output to improve the basic shape factor so a hot tube is needed to make up for loss. National took that to an extreme in the HRO-60 and slightly less in the NC-183D.

7. In a relatively KISS circuit with no decent front end consider a single stage of dual conversion using whatever crystal you have available in the 1700-2500 kHz range as an example Ive had good luck with.

8. If you want a decent platform to start with use a dirt cheap SX-140 which has plenty of room to play in even for double conversion; Ive done those to 262 and 455 kHz

Carl
Logged
N2DTS
Member

Posts: 725




Ignore
« Reply #9 on: November 09, 2017, 08:54:22 AM »

I have not had any issues with image rejection at all in 10 years of using my single conversion 455 KHz IF receivers.
I do have a high Q preselector setup between the antenna input and the mixer, and that seems to work well.

My simple home brew receivers outperform anything else I have tried for what I made them for, they pull out weak signals better, have less noise, handle impulse noise better, do not have spurs or images, and have the best fidelity.

I have had:
R390a (high noise),
flex 1500, 3000, 5000 (the 5000 was quite good),
SX17,
Scott SLRM,
Peabury V2 sdr (quite good for a very small amount of parts),
QS1R (very good but too much USB port latency)
Elad fdm-duo (wacky radio),
RF space sdr-iq (good but high noise),
Anan10E (good),
Anan 100B (good),
Icom 7300 (limited freq response, prone to impulse noise, some built in noise),

And a lot of older receivers in the past, nc300/303, 75A4, 51S-1, 75s-1, FT102, icom 756pro 3, etc.

On 160 to 40 meters where I operate mostly, the home brew receivers work as well as or better then anything else.
Don't let someone make you think you need a complex or fancy circuit to get great results.
That may be true above 20 meters, but not below that.
Some designs ended up complex because they were designed to tune from 600 KHz to 30 MHz with a poor antenna and minimal operator adjustments. That would add more (noisy) conversions, multi rf amplifiers and gain problems.
Modern rigs like the icom 756 pro series did FM and up to 6 meters so had a poor 70 MHz 1st IF and a poor 15 KHz filter (to allow FM) and have problems handling strong close signals. They also had a lot of phase noise and high gain IC chip hiss.

Fix one problem and cause others....

Logged
WB6BYU
Member

Posts: 17046




Ignore
« Reply #10 on: November 09, 2017, 02:00:38 PM »

Quote from: N2DTS

On 160 to 40 meters where I operate mostly...



Then consider using some standard crystals around 4.5 MHz (4.4336 is common, others are stocked at
50 cents apiece through Mouser and Digikey, etc.) for an IF filter with a VFO at 2.0 to 2.3 MHz. 
Gives inverted tuning, but covers both bands with a single VFO.

G3VA's Amateur Radio Techniques shows a number of circuits for using crystal filters with tubes.
One refers to an article in QST for February 1958 where one crystal is used in each of several
cascoded stages.  Or W6MTY's circuit (from CQ, issue not mentioned) using switched crystals to set
the bandwidth, followed by a crystal-controlled regenerative detector as a "super-gainer".  You can use
the IF transformers from TV sets in that frequency range.

Or reverse the circuit, using a single 4.5 MHz crystal in the first oscillator and follow it with a 2.0 - 2.5 MHz
tunable IF and/or single conversion receiver, that could also be used with similar converters for other
bands (a 1.5 MHz or 6 MHz crystal would cover 80m, 12 MHz for 30m and 20m, etc.)  That way you don't have to
bandswitch your VFO, which I have found to be a common source of instability (at least in an inexpensive
receiver.)
Logged
KL7CW
Member

Posts: 255




Ignore
« Reply #11 on: November 09, 2017, 08:15:32 PM »

ED,
     Congratulations on your proposed project.  The most fun I have ever had in my 63 years is building and sometimes designing (or usually lifting parts of the project from other designs).  BYU has a good point to include a crystal filter in your design.  It is fun and not too difficult to build your own crystal filter, especially if you are satisfied with something that just works reasonably OK.  Crystal filters roughly in the 4 to 9 MHz range are inexpensive to build and can give satisfactory results for casual CW and SSB.  Filters in roughly this area of the spectrum can be sharp enough for most CW operation, yet can be widened out for OK SSB performance....not sure about AM.   Carefully choose your IF frequency to avoid (as much as possible) most images and other spurious signals. (there are internet sites and programs you can play with to see about possible good or poor choices for IF frequencies.
    For example a few years ago I wanted to build a project which required an IF frequency in about the 7.4 MHz region. I bought 25 crystals from Mouser for about $10 I think.  I tested them all in a simple oscillator circuit, they all worked, and I got about 3 or 4 groups of 3 crystals which were very close in frequency (I think within about 10 or 20 Hz).  This was for a simple portable rig, so I just copied the 3 crystal filter circuit used in my Elecraft KX-1.  Now 4 crystals would have been better, but the 3 crystal version suited my need.  Like the 4.9 mHz Elecraft filter my roughly 7.4 MHz filter did a satisfactory job for CW and SSB seemed OK, I could adjust the BW by just adjusting a pot. which controlled the voltage on 3 vari cap diodes.  A tracking spectrum analyzer would have been very handy, but my analyzer was not working....so I just improvised.  Not too hard...took a bit of time.  A few of the crystals not earmarked for filters were close enough to use for BFO crystals (with a bit of C or L, I believe). If you use a crystal filter..it is not necessary to use hi Q IF transformers for selectivity....in fact I think I just wound a small toroid coil for the input and output if I remember correctly.  Now if you are a perfectionist you need to consider things like input and output Z, group delay, etc. etc. but this is ham radio, build, operate, tear it apart, rebuild, etc. have fun.  I was just giving the KX 1 filter as probably the simplest reasonable filter, for sure there are better filters to buy or build.  A very good resource for any home builder is a publication called "Experimental Methods of RF design", It may still be available from the ARRL,  It is my most used book by far.  I am not sure if Experimental Methods.....has any or many vacuum tube circuits.
                Rick  KL7CW
Logged
N2DTS
Member

Posts: 725




Ignore
« Reply #12 on: November 10, 2017, 05:27:23 AM »

The filters I have work fantastic, the Kiwa standard filter modules.
Not sure what they can make these days but they made getting a very good filter easy.
Its a very small module with pig tails, and it runs on 6 to 30 volts.
I think its some op amp into three slightly different ceramic filters then out into another op amp.
Since the filters look into op amps, the Q is high I guess, and since everything is in a very small cube, the selectivity curve is very sharp.
Easier to do at 455 KHz I guess.

http://kiwaelectronics.com/kiwa455.html

I rate them as good as sdr filters and better then mechanical filters.


Quote from: N2DTS

On 160 to 40 meters where I operate mostly...



Then consider using some standard crystals around 4.5 MHz (4.4336 is common, others are stocked at
50 cents apiece through Mouser and Digikey, etc.) for an IF filter with a VFO at 2.0 to 2.3 MHz. 
Gives inverted tuning, but covers both bands with a single VFO.

G3VA's Amateur Radio Techniques shows a number of circuits for using crystal filters with tubes.
One refers to an article in QST for February 1958 where one crystal is used in each of several
cascoded stages.  Or W6MTY's circuit (from CQ, issue not mentioned) using switched crystals to set
the bandwidth, followed by a crystal-controlled regenerative detector as a "super-gainer".  You can use
the IF transformers from TV sets in that frequency range.

Or reverse the circuit, using a single 4.5 MHz crystal in the first oscillator and follow it with a 2.0 - 2.5 MHz
tunable IF and/or single conversion receiver, that could also be used with similar converters for other
bands (a 1.5 MHz or 6 MHz crystal would cover 80m, 12 MHz for 30m and 20m, etc.)  That way you don't have to
bandswitch your VFO, which I have found to be a common source of instability (at least in an inexpensive
receiver.)
Logged
KM1H
Member

Posts: 2458




Ignore
« Reply #13 on: November 10, 2017, 02:12:31 PM »

The last crystal filters I bought were a set of 3 widths at 500 kHz from a Racal receiver. Very reasonable on Fleabay and shipped from Greece some 4-5 years ago.
Logged
N2EY
Member

Posts: 4436




Ignore
« Reply #14 on: November 16, 2017, 12:45:40 PM »

The last crystal filters I bought were a set of 3 widths at 500 kHz from a Racal receiver. Very reasonable on Fleabay and shipped from Greece some 4-5 years ago.

Were they like these ones from Yugoslavia?:

https://www.ebay.com/itm/250Hz-CW-CRYSTAL-FILTER-for-500KHz-IF/322858189803?hash=item4b2bd903eb:g:eSAAAOSwGUBZ-YnS

https://www.ebay.com/itm/5-KHz-AM-CRYSTAL-FILTER-for-500KHz-IF/322858152878?hash=item4b2bd873ae:g:c4UAAOSwcUBYG8u1

https://www.ebay.com/itm/2-7-KHz-SSB-crystal-filter-for-500-Kc-IF/302117797917?_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D2%26asc%3D41376%26meid%3D4cc5cfaee52f41069709eb79bf86e91b%26pid%3D100005%26rk%3D2%26rkt%3D6%26sd%3D322858189803&_trksid=p2047675.c100005.m1851

https://www.ebay.com/itm/6-KHz-AM-crystal-filter-for-500-Kc-IF/302117796347?hash=item46579fb9fb:g:7lYAAOSwNuxXX71K

https://www.ebay.com/itm/250-Hz-CW-narrow-crystal-filter-for-500-Kc-IF/332013416760?hash=item4d4d8ab138:g:jikAAOSwMVdYDzMB

Logged
Pages: [1] 2 Next   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!