Construction of a Receiver

[N0WVA]

I am constructing a receiver to receive the AM guys on 80 and 160. I will probably add a product detector after I get it perculating. I want to use it with my Central Electronics 20A, which I picked up recently at a hamfest.

I thought I might make postings and pictures here of my progress, and maybe everyone could throw in ideas or improvements.

The goal is to build a simple AM receiver with AGC and a 455khz IF, then experiment with different filters, and perhaps trying to homebrew a mechanical filter( if its possible).

I already etched a PC board for the mixer, and am stuffing it now. Will post pictures and schematic in a while.

Lets have some homebrew fun.

Doug

[kl7aj]

Quote[/b] (N0WVA @ May 10 2006,09:22)]I am constructing a receiver to receive the AM guys on 80 and 160. I will probably add a product detector after I get it perculating. I want to use it with my Central Electronics 20A, which I picked up recently at a hamfest.

I thought I might make postings and pictures here of my progress, and maybe everyone could throw in ideas or improvements.

The goal is to build a simple AM receiver with AGC and a 455khz IF, then experiment with different filters, and perhaps trying to homebrew a mechanical filter( if its possible).

I already etched a PC board for the mixer, and am stuffing it now. Will post pictures and schematic in a while.
#
Lets have some homebrew fun.

Doug
Congratulations on your receiver project AND your 20A. I had a 100V once, which I'm still kicking myself over selling. What an amazing, ahead-of-its-time marvel!

eric

[KF0RT]

Quote[/b] (N0WVA @ May 10 2006,10:22)]I thought I might make postings and pictures here of my progress, and maybe everyone could throw in ideas or improvements.
Absolutely! I wanna see!!! http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif

73, Rob

[N5RLR]

Really! I do too! http://www.qrz.com/iB_html/non-cgi/emoticons/wink.gif

'WVA, What are you using for PC-board layout and etching?

Also, there are methods for using loose-tolerance crystals as elements in filter networks, in the Amateur literature. Check ARRL handbooks, online, etc.

Good show! http://www.qrz.com/iB_html/non-cgi/emoticons/laugh.gif

[KA4DPO]

Sounds like a fun project to me. I love homebrew........

[AK7V]

I would certainly like to follow along!

[W4HAY]

This is going to be a vacuum tube project, isn't it?

Seriously, for selectivity, what about a Q-multiplier?

[W5HTW]

Yes, sounds like lots of fun! I wish I had that ambition these days. I built two tube-type receivers in my whole 50 years in this hobby. In my dreams I may build another one. But that's about the only way! Shame to get old and on a fixed income. Darn. (Well, good excuse, anyway.)

Yep, have fun.

Ed

[wa9cwx]

Fantastic!

Please keep us updated, and have fun......

PS....Why NOT tubes....just wondering..... personaly I would think a TRF receiver would be neat, probably not as easy to get good filtering, but not sure what you really need for AM, although would probably have been more practical 60 years ago, http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif

Anyway, best of luck with it !

[ky5u]

Quote[/b] (KF0RT @ May 10 2006,11:18)]Quote[/b] (N0WVA @ May 10 2006,10:22)]I thought I might make postings and pictures here of my progress, and maybe everyone could throw in ideas or improvements.
Absolutely! I wanna see!!! http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif

73, Rob
Love the avatar. Looks like there's a trailer hitch with most of the chrome missing somewhere in your driveway.

[N0WVA]

Ok, heres the mixer schematic.

[img=http://img99.imageshack.us/img99/6727/mixer1lw.th.jpg] (http://img99.imageshack.us/my.php?image=mixer1lw.jpg)

Im taking a picture of the board now.....

[img=http://img105.imageshack.us/img105/9563/image096ut.th.jpg] (http://img105.imageshack.us/my.php?image=image096ut.jpg)

[w8cbc]

I did one a lot like that about 20 years ago to mix SW down to a MWBC receiver. A preselector circuit is essential.

[N0WVA]

Quote[/b] (kl7aj @ May 10 2006,10:17)]Quote[/b] (N0WVA @ May 10 2006,09:22)]I am constructing a receiver to receive the AM guys on 80 and 160. I will probably add a product detector after I get it perculating. I want to use it with my Central Electronics 20A, which I picked up recently at a hamfest.

I thought I might make postings and pictures here of my progress, and maybe everyone could throw in ideas or improvements.

The goal is to build a simple AM receiver with AGC and a 455khz IF, then experiment with different filters, and perhaps trying to homebrew a mechanical filter( if its possible).

I already etched a PC board for the mixer, and am stuffing it now. Will post pictures and schematic in a while.
#
Lets have some homebrew fun.

Doug
Congratulations on your receiver project AND your 20A. #I had a 100V once, which I'm still kicking myself over selling. # What an amazing, ahead-of-its-time marvel!

eric
Hoping to fire it up in a few weeks. Got a real good deal on it at a local hamfest!

[WA5KRP]

I'm impressed. Did you design the circuits?



WA5KRP
Texas

[N0WVA]

Quote[/b] (N5RLR @ May 10 2006,13:24)]Really! #I do too! http://www.qrz.com/iB_html/non-cgi/emoticons/wink.gif

'WVA, What are you using for PC-board layout and etching?

Also, there are methods for using loose-tolerance crystals as elements in filter networks, in the Amateur literature. #Check ARRL handbooks, online, etc.

Good show! http://www.qrz.com/iB_html/non-cgi/emoticons/laugh.gif
Using ferric chloride from the Radio Shack. Picked up some PC board on the cheap at Gateway Electronics in St.Louis. I also loaded up on about 50 little drill bits at the Electronics Exchange, to my surprise, they fit right in my battery powered dremel!

Im using the sharpie marker for the resist and drawing it by hand.

Might try that crystal filter. I have some 500 khz crystals. Think they will be too sharp to use at that freq.? Might have to raise the IF frequency to use crystals.

[N0WVA]

Quote[/b] (W4HAY @ May 10 2006,18:49)]This is going to be a vacuum tube project, isn't it?

Seriously, for selectivity, what about a Q-multiplier?
Good idea, Id like to try it with the MOSFET.

[N0WVA]

Quote[/b] (WA5KRP @ May 11 2006,18:48)]I'm impressed. #Did you design the circuits?



WA5KRP
Texas
The mixer is pretty standard, I think its in the Handbook, but I cobbled this one up from memory. I used it in my BCB receiver I built a while back and really liked how it performed in spite of its simplicity. By the way, I am using the MFE201 because I got a good deal on them on EBAY, and after swapping one out with a 40673 in my regen, they performed just as well, although they needed a little less voltage on gate 2 to achieve the same gain. Something like .5 volts, where the 40673 was a little over a volt. We will see how it works as a mixer....

[N0WVA]

Quote[/b] (kd8bsr @ May 11 2006,18:34)]I did one a lot like that about 20 years ago to mix SW down to a MWBC receiver. #A preselector circuit is essential.
Im wanting to do a single tuned front end, like the old tube radios. Hoping a 365 pf cap will tune 3.5-1.8.

[W4HAY]

You're going to be fighting strong signals from the BC band. Consider a circuit the crystal set crowd refers to as the #Tuggle Tuner (http://www.schmarder.com/radios/tech/te-part2.htm). It's especially efficient and selective if the coupling between the primary and secondary is made variable, and either spiderweb or basketweave coils made of Litz wire are used. Not only do the coils work good, they look really cool, especially if you take your time and do a neat job.

Matter of fact, why not go to The Crystal Set Society forums (http://www.midnightscience.com/rapntap/default.asp) and log in? These guys (and gals) are very creative when it comes to getting the most out of tuned circuits, and welcome fellow homebrewers.

[w8cbc]

I missed the fact that it's just for 160 and 80 metres. Also that the cap is variable. No excuse - I'm unobservant. http://www.qrz.com/iB_html/non-cgi/emoticons/smile.gif

That circuit I slapped together back-when brought some very interesting SWBC into the Sansui quad receiver. I wound up putting together a tunable BFO (440-470 kc) for it as well. That ol' stereo (I still have it) has had a lot of strange things done to it over the years. http://www.qrz.com/iB_html/non-cgi/emoticons/smile.gif

[W4HAY]

Stumbled across this Q-multiplier schematic (http://web.telia.com/~u85920178/use/qmult.htm) this afternoon!

[N0WVA]

OK, I got the IF stage done, and I decided to tack some stuff together. I got a MPF102 running as a HArtley, that is the L.O.

The ant goes to a single tuned front end, mixes in the MOSFET with the LO, then goes to a TOKO 455 transformer. Then into a Murata ceramic resonator I stole from a CB, then back into another TOKO transformer. Another MOSFET amplifies the signal then drives a 1N34 right off its source. That goes to a 2N3904 audio amp. An , man....I got ear shattering audio from a pair of 2000 ohm phones, its just unbelievable something this simple works so well. Only one thing.....selectivity is only around 10 Khz.....

Im now looking at the Q-Multiplier......But I have one question, will the AGC voltage have an adverse affect on the selectivity?

I read that the Drake 2b has a Q multiplier, but do they apply the AGC to that same stage, and does it have any adverse affects?

Thanks....Doug

[N0WVA]

Noticed a problem tho when fiddling around with AGC voltages....this MFE201 MOSFET likes around .5 volts on it to develop full gain.....0 volts reduces it quite a bit, so I stuck reverse bias on gate 2 with a 1.5 volt battery, so at - 1.5 the MOSFET cuts off quite well.......Im thinking its gonna be hard to develop an amplified AGC volatage that swings negative without using some kind of special power supply....

[W4HAY]

Many circuits use an AGC amplifier stage (or two), which can also perform inversion if needed.

This (http://www.elecdesign.com/Articles/Index.cfm?AD=1&AD=1&AD=1&AD=1&ArticleID=6272) may give you some ideas!

[kl7aj]

Quote[/b] (N0WVA @ May 16 2006,20:38)]OK, I got the IF stage done, and I decided to tack some stuff together. I got a MPF102 running as a HArtley, that is the L.O.

The ant goes to a single tuned front end, mixes in the MOSFET with the LO, then goes to a TOKO 455 transformer. Then into a Murata ceramic resonator I stole from a CB, then back into another TOKO transformer. Another MOSFET amplifies the signal then drives a 1N34 right off its source. That goes to a 2N3904 audio amp. An , man....I got ear shattering audio from a pair of 2000 ohm phones, its just unbelievable something this simple works so well. Only one thing.....selectivity is only around 10 Khz.....

Im now looking at the Q-Multiplier......But I have one question, will the AGC voltage have an adverse affect on the selectivity?

I read that the Drake 2b has a Q multiplier, but do they apply the AGC to that same stage, and does it have any adverse affects?

Thanks....Doug
If that ceramic filter doesn't rot your socks off, you can build a nice half-lattice crystal filter. There used to be quite a few half-lattice filters using C B crystals, once upon a time. You can also 'speriment with a crystal phasing arrangement....all the best features of a q-multiplier and a crystal filter all rolled into one chewy morsel.

:P

eric

[WA7KKP]

I question the need of a product detector -- as it works only with a BFO, best for SSB and CW. All you need is a diode detector for AM . . . Or maybe getting exotic a synchronous detector if you want hi-fi audio?

Gary WA7KKP