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Old 1st Jun 2021, 7:19 pm   #1
Spencervs
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Default Building my first shortwave radio

Hello everyone! So I have become interested in building a small regenerative receiver that will be hopefully inexpensive (I don't have loads of parts spare to hand) and easy enough to source parts I need. This will be my first proper project next to my successful capacitor reformer!

Before I do, I have some novice questions... Will the following two circuits (one a 2 tube. 'DX-er' and the other a 3 tube 'ocean hopper') be able to pick up much? I would love to hear some far away stations if possible and maybe even some small amateur local ones. I am aware though that I am late to the party with many radio stations going digital!

I do not have a house with a garden to make a huge antenna many metres in the sky to help find these signals and so would probably need to use some kind of loop antenna... So would either of these radios meet the mark? If so, I may need to post some help requests in the "wanted" section to find some relevant parts!

Thanks in advance!
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Old 1st Jun 2021, 7:35 pm   #2
Cruisin Marine
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Default Re: Building my first shortwave radio

Aerial is king!
Get the antenna good as possible and you will have a ball!
I have an old Cossor TRF I use at times, even now it holds up well in to a decent long wire.
I love it- this is REAL RADIO!
Good luck

PS: I used to know Grove Park well, used to live down the road, used to see Souxsie Soux from the Banshees outside the station a lot and in the Baring Hall pub was it across the road?
Remember it was Ind Coope back in the day.
I bet the bus park/station is still there?
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Old 1st Jun 2021, 7:36 pm   #3
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Default Re: Building my first shortwave radio

Be aware that there's rather less going-on on shortwave these days than what was the case back in the days when your suggested receivers were designed.

Most of the nation-state AM broadcasters have closed-down; equally, us radio-amateur types have switched to using SSB and digital-modes - while a 'regen' can resolve SSB it's not going to be much use to resolve FT8 etc unless hooked-up to a computer; equally, SSB voice and digital-modes need serious frequency-stability in the receiver - old-style regen radios, with hand-capacity and swaying-in-the-wind antenna issues are really not going to be fun.

If you want a suggestion for a regen receiver which works rather well despite modern compromises, I can recommend the "Valve/Transistor Short Waver" from July 1961 Practical Wireless. You can avoid the transistor-bit by using an ordinary valve output-transformer in the anode circuit and feeding a pair of WWII-era "DLR" headphones.

Such a receiver got me listening on 80 Metres SSB back in the 70s, using a battery-filament valve salvaged from the local tip.
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Old 1st Jun 2021, 8:08 pm   #4
merlinmaxwell
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Default Re: Building my first shortwave radio

Here https://www.vintage-radio.info/books number three "A beginners guide to radio" I would go for the medium wave one first, there is still something there.
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Old 1st Jun 2021, 8:54 pm   #5
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Default Re: Building my first shortwave radio

Could I offer you an alternative design, which I can confirm works very well indeed http://vintageradio.me.uk/radconnav/2_valve.htm. This radio uses the same valves (DF91 are equivalent to 1T4).

I used to use an aerial of about 30ft of wire strung around the loft; anything less will be "uncertain". The coils can be changed to "hit" whatever frequencies you decide you want. One other problem you need to anticipate is that the high-voltage batteries specified for the valves are no longer made. One possible solution to that is to wire up a whole bunch of 9V PP3's in series, but there are other solutions.

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Old 1st Jun 2021, 9:32 pm   #6
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Default Re: Building my first shortwave radio

I think you'll find the one that Baz suggests easier to get working and probably easier to follow the circuit. DF91's are easy to source but remember you'll need to make up an HT supply with series connected PP3's (either 7 or 8 of them with this circuit). Also remember that these little battery valves are very delicate and you need to be VERY careful not to create shorts between HT and LT otherwise it's goodbye valve....

With care this should be a great little set to get you started. The advantage is that it uses home wound coils rather than commercial coils which would be difficult to source now. Give it a go! Once you have built your first radio successfully, it gives great confidence for the next and also helps you understand how radio's work.

You do need a good longwire aerial though. You should be able to get reasonable results from an aerial around the room. I also didn't have access to a garden but I was able to hook a longwire from my brother's bedroom window down to my workroom which was actually about 25 feet and I got brilliant results from that.
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Old 2nd Jun 2021, 6:26 am   #7
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Default Re: Building my first shortwave radio

Ah thank you for the replies! I was keen on using a circuit that uses a DL91 as I have one already! I also factored that I like the idea of plug in coils as it might be fun to make a medium wave coil or maybe even experiment with an FM coil (possible?). I noticed on the last circuit described that it uses fixed coils, can that be converted to plug in ones? If so how?

It also uses two DL91s but is there a way to substitute one of them for any of the following:

DK96
DL96
DF96
DF94

I have a spare of each of these so that would keep the cost down.
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Old 2nd Jun 2021, 6:35 am   #8
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Default Re: Building my first shortwave radio

Quote:
Originally Posted by Cruisin Marine View Post
Aerial is king!
Get the antenna good as possible and you will have a ball!
I have an old Cossor TRF I use at times, even now it holds up well in to a decent long wire.
I love it- this is REAL RADIO!
Good luck

PS: I used to know Grove Park well, used to live down the road, used to see Souxsie Soux from the Banshees outside the station a lot and in the Baring Hall pub was it across the road?
Remember it was Ind Coope back in the day.
I bet the bus park/station is still there?
That's fantastic, I love siouxsie soux! I knew someone who's mother went to the same school at the same time as her. According to some old photos I have seen, Grove Park hasn't changed much at all. I live in one of the flats built for the station workers back in the 30s, I think you would see many familiar sights and have no trouble getting around. Sadly the Baring Hall Hotel had a fire I believe in the 2000s and nearly burnt away but was restored and opened again. Covid seems to have dealt a fatal blow now though as it hasn't been open since last March... So let's see what form it takes in the future when someone hopefully takes it on (it's grade II listed).
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Old 2nd Jun 2021, 4:22 pm   #9
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Default Re: Building my first shortwave radio

Quote:
Originally Posted by Spencervs View Post
Ah thank you for the replies! I was keen on using a circuit that uses a DL91 as I have one already! I also factored that I like the idea of plug in coils as it might be fun to make a medium wave coil or maybe even experiment with an FM coil (possible?). I noticed on the last circuit described that it uses fixed coils, can that be converted to plug in ones? If so how?

It also uses two DL91s but is there a way to substitute one of them for any of the following:

DK96
DL96
DF96
DF94

I have a spare of each of these so that would keep the cost down.
Hang on!! That circuit you posted (and the one that Baz posted) uses 1T4 (DF91), You mention two DL91....OK firstly DL91 is an audio output valve (L denotes output pentode). The DF91 is an RF/IF pentode (F denotes small signal pentode). The DL91 would not work very well as an RF/IF pentode....just not designed for the job. Make sure you have DF91's! If you have DL91's you are going to fall at the first hurdle!

As to your second question, the DF94 or DF96 could probably be substituted since they are very similar and fine if the filaments are connected in parallel. Personally I would suggest you don't try any substitutes at this early stage in your learning. Best to stick with a tried and trusted design and get that working first. By all means try substitutes afterwards when you have more knowledge as then you can probably decide what needs to be done regards rewiring, changing component values etc.

The problem with substitutes is that there is always a chance that the chosen sub may not work at all or may not work very well. If you sub before the original circuit is built, you will never know if poor/no operation is caused by the sub or by a wiring/component error.

If you are lacking DF91's I'm quite sure that members here will be only too happy to set you on the road by supplying a couple of good 'pulls' (good second-hand ones)! I'll also have a look in my stash when next in the workshop.

FM? Not with that circuit or those valves. FM is a whole new ball-game. Yes a TRF FM receiver is possible but requires careful construction to make it work well. Stick to MW/SW before even considering an FM set.

Start hunting out the rest of the components!


PS...No reason why you couldn't add a DL91 to provide loudspeaker output making it a 3 valve set.....but leave that for later!
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Old 2nd Jun 2021, 4:50 pm   #10
merlinmaxwell
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Default Re: Building my first shortwave radio

Quote:
Hang on!!
Those regen circuits are very (very very) tolerant of what valve is used, anything with a bit of gain will work, the F. G. Rayer book I mentioned even straps a pentode to triode.
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Old 2nd Jun 2021, 5:45 pm   #11
Restoration73
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Default Re: Building my first shortwave radio

The 1T4 circuit on p.34 works, and used Denco green plug in coils (these
were made in octal and B9A versions) and could also be used with a single
valve e.g. DL92 audio amplifier stage for loudspeaker.

http://www.g4dmp.co.uk/dencocoil.pdf
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Old 2nd Jun 2021, 5:52 pm   #12
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Default Re: Building my first shortwave radio

Quote:
Originally Posted by merlinmaxwell View Post
Quote:
Hang on!!
Those regen circuits are very (very very) tolerant of what valve is used, anything with a bit of gain will work, the F. G. Rayer book I mentioned even straps a pentode to triode.
Remembering that he's very limited in his aerials, I too think he should build to the spec or risk disappointment.

B
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Old 6th Jun 2021, 1:26 pm   #13
Spencervs
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Default Re: Building my first shortwave radio

Thank you all for the input. So I have as you may have seen posted a request for some of the parts that I am interested in buying from members if they have spares that I am unable to source from new. The only other part as yet I am unsure of is the RF choke. It mentions denko type rfc5? What is this and is there a modern type I can get?
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Old 6th Jun 2021, 4:37 pm   #14
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Default Re: Building my first shortwave radio

The RF choke can be a) not used at all or b) be a 1k (very approximate) resistor. As I said these sets are very tolerant of component choice and given the much higher output of modern transmitters almost anything will work.
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