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14th Jun 2008, 12:37 pm | #1 |
Dekatron
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
Posts: 5,765
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"Hikers' Two" advice?
Hi guys,
Thanks for reading this. I posted this message in the "parts wanted section" but pondered on whether the "Homebrew" section might have been a better place. My posting was viewed many times but didn't elecit any replies, so I thought I'd try my luck and re-post it here. I'm aiming to make a replica "Hikers' Two" receiver as illustrated on the link here: http://oldradios.co.nz/hikers/kb7nrn/index.htm I've gathered most of the bits I need (valves and bases, coil formers/base, etc) except for the dial and interstage transformer. I know these dials were very commonplace and have often seen them at - for example, the NVCF, so hopefully, somone on here might have one (in black)they'd be happy to part with for an appropriate sum. Also, a little knob similar to the reaction control knob too, perhaps? In the set that John Bauman (the writer of the article on the "Hikers' Two") constructed he refers to using a small power transformer, which fortuitously had the right ratio of 3:1 to function as an interstage transformer. To quote the author: "The transformer used in this project wasn’t made for audio, it’s a little power transformer with a secondary of 150vac @ 50ma, pretty small. I measured the resistance and inductance; found that it was close to an interstage audio transformer so I used it. Any interstage transformer from 2:1 to 5:1 ratio should work fine". (End quote). It would be nice to try to use a genuine inter-stage transformer if anyone has one to hand which might suffice, but failing that, any advice and enlightenment on what might suit as a substitute would be much appreciated. It isn't on view, so as long as it's small and does the job, that's really all that matters. Any advice would be much appreciated. Regards, David, G4EBT |
15th Jun 2008, 11:51 am | #2 |
Triode
Join Date: Mar 2007
Location: Round Lake Park, IL. USA
Posts: 30
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Re: "Hikers' Two" advice?
I've seen a small 120 volt primary to 6.3volt secondary filament transformer used in a lot of cases. It appears to be a lot closer to 3:1 ratio. Radio Shack use to carry that transformer although in the UK it might be a 220 volt primary.
Hope this helps. 73 de Gary, KF9CM
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17th Jun 2008, 9:50 am | #3 |
Dekatron
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
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Re: "Hikers' Two" advice?
Thanks for reading my request and for your helpful reply Gary.
Amazing how many times some of these positng are read! Regards, David G4EBT (Still looking for the dial!) |
17th Jun 2008, 1:07 pm | #4 | |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
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Re: "Hikers' Two" advice?
Quote:
I would expect the lack of primary (ie low voltage side in this application) inductance on a little mains transformer would have a marked effect on the low frequency audio performance. Maybe a 240V to 55-0-55V (use half the secondary as the audio primary) would be better if you can find a low power rating unit. |
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17th Jun 2008, 5:34 pm | #5 |
Retired Dormant Member
Join Date: Mar 2007
Location: Skelleftea, Sweden
Posts: 250
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Re: "Hikers' Two" advice?
as long as ratio is 1:3-1:5 and it is not too large physical size (i use bogenit should work ok.
i use a Bogen t-725 om mine, http://schmarder.com/radios/misc-stuff/t-725.htm. |
17th Jun 2008, 8:35 pm | #6 |
Dekatron
Join Date: Sep 2005
Location: Seaford, East Sussex, UK.
Posts: 5,997
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Re: "Hikers' Two" advice?
The real things come up on ebay quite regularly (there are a couple at the moment) but do get the seller to check both primary and secondary have continuity.
I would have to read up on tx equivalent circuits but using a mains tx with a high impedance circuit doesn't sound like a good idea. The Ferranti AF5 I keep meaning to rewind was clearly designed to be low capacitance. Have you tried an ad in the WANTED section? |
21st Jun 2008, 11:03 pm | #7 |
Triode
Join Date: Mar 2007
Location: Round Lake Park, IL. USA
Posts: 30
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Re: "Hikers' Two" advice?
Sorry, I haven't been on here in a few days.
As far as 19:1 ratio goes, that's true if you look at the voltage ratio. If you measure the impedance, ( excuse me while I whip out the old Autek), of the the primary and secondary of the 6.3 volt filament transformer, one gets approx. 1980 ohms on the primary and 380 ohms on the secondary. That works out to about 5:1. The Radio Shack 110 v to 6-0-6 volt transformer is around 3:1. Try it out, there cheep as chips and if it doesn't quite meet your standards, you can pay more for the "old, rare" ones on eBay. Trying to help, Gary, KF9CM
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21st Jun 2008, 11:38 pm | #8 |
Moderator
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Location: Ipswich, Suffolk, IP4, UK.
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Re: "Hikers' Two" advice?
Surely transformers are specified by their turns ratio. The IMPEDANCE ratio will be the square of this. The ratio of primary RESISTANCE to secondary RESISTANCE doesn't matter much. These figures are only included in service sheets so that a transformer can be easily tested for shorted turns.
The mains transformer described in post one would have had a turns ratio of about 250/150 or 1.66 to 1. This is a bit different from the 2 :1 to 5:1 suggested.
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22nd Jun 2008, 2:34 am | #9 |
Retired Dormant Member
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Location: Salt Spring Island, BC, Canada
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Re: "Hikers' Two" advice?
It would be better to use an interstage transformer if you can find one. Small power transformers might have a suitable turns ratio but they are optimised for 50 cps and have high interturns capacity which will cut down the audio high frequency response of the receiver.
John. Last edited by JHGibson; 22nd Jun 2008 at 2:35 am. Reason: spelling |
26th Aug 2008, 12:34 am | #10 |
Rest in Peace
Join Date: Dec 2007
Location: Doncaster, South Yorkshire, UK.
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Re: "Hikers' Two" advice?
hi.
I've also built this little set and its very good. I used the 1Q5 vales though. Why did we use leaky grid when this way was better!. Pete G4MRU |
26th Aug 2008, 7:48 pm | #11 |
Dekatron
Join Date: Sep 2005
Location: Seaford, East Sussex, UK.
Posts: 5,997
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Re: "Hikers' Two" advice?
Although it's a regen, I guess it rectifies the signal on the grid? I am sure I have read that this kind of aerial coil regen was outlawed by the BBC as it makes a good transmitter.
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27th Aug 2008, 1:00 am | #12 |
Rest in Peace
Join Date: Dec 2007
Location: Doncaster, South Yorkshire, UK.
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Re: "Hikers' Two" advice?
Rats.. Just had to be something like that. But all regens did that.
Pete |
28th Aug 2008, 11:21 pm | #13 |
Rest in Peace
Join Date: Dec 2007
Location: Doncaster, South Yorkshire, UK.
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Re: "Hikers' Two" advice?
hi
I've built this hickers 2 and it works well. Now I'm going to build the SW version of it. The thing is can I use a PARAFEED in place of the inter stage transformer! Hope so, first I've made the box and tin work and second, It cost 8'6 when new.. Pete |
30th Aug 2008, 11:21 am | #14 | |
Retired Dormant Member
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Re: "Hikers' Two" advice?
Quote:
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