Shortwave Receiver Project
Brett Hall
receiver. I understand a mixer and local oscillator circuit(s) should
accomplish this end.
Though I have found a few general circuit schematics - I am finding a lack
of information on procedures for actual component selection and calculation,
JFET biasing, etc...
Any suggestions on what steps to take next would be greatly appreciated.
Thanks in advance for your help.
Best wishes,
Brett
KB2IBD
Brett Hall
Brett Hall
Brett Hall
Mark Fraser
"get there from here" as it's taking you to learn about multiple posting.....
We've seen your request, and the answer you don't want to hear is:
"You could, but it isn't likely to be much good for anything".
I'll sell you an "inexpensive AM/FM/SW" receiver for $10.00 that will outperform
anything you could do by butchering an am/fm....
/mark
Grogancat
we can go down to the drug store and pick up
a radio that will outperform anything we can
make or modify.
My forte is building tube and solid state radios,
winding my own if transformers, rf coils, osc coils etc...
In my opinion, the poster should start first with
an old am tube type radio... all american five line up, either octal or 9 pin
miniature just to get better angle at the parts. Select a bandspread and
knowing the circuit configuration, simply re-wind your rf and osc
coil(s). I have done this, in fact the old USN
TCS series receivers were nothing but AA5
type of circuits using octal 6sk7, 6sn7 etc..with
proper band and osc coils but keeping the
455 kHz IF. They arent the best performers,
but again, the point is to have fun and learn.
As far as taking a standard modern am/fm radio,
I think you would be hard pressed to get at most of the miniature components
easily, as well you are looking at converting osc and band coil(s) which are
small enough already
and re-winding them. you wont easily find any commercially wound rf and band
coils for that
particular radio. You can buy small coil parts
and kluge new coils etc.... using wire so fine you can hardly see it..... It
might be easier to
build a converter, these are sold as kits and
introduces another level of conversion..I saw one advertised to use with a
standard am car radio. I dont think you would need to do anything to any of
the BJT or JFET biasing,
you are really only changing the osc and rf
freqs at the front end and should leave the
IF strip alone if you do attempt to modify a
modern am/fm radio.
Anyway, thats my 2 cents.
Have fun.
Your fellow radioman and marconi-man
Tony
"what good is it?"
.....it's coming from out there...
"out where?"
.....space....
"just space? You've spent thousands of dollars on
transistors..and..and..circuits
and cathode ray...what good is it?"
.....well........it's interesting.....
Butch Magee
Butch KF5DE
Jim
band?
Let's see...530 to 1600KHz on the BCB. Using a 10 MHz crystal would give
you 10.53 to 11.6 MHz reception.
Better yet, use a VFO for the conversion oscillator and you can select
whatever band you want. I used to have one of these for SW use with my
Drake B line (receive only!) and it worked fine--just plug it into one of
the spare band select crystal sockets.
Jim
N8EE
MervinS
sites with the information you seek. Suggest you start with
http://hem2.passagen.se/sm0vpo/#rx. Scotty
Grogancat
>
Im not trying to discourage him, just suggesting a starting point. It might
build
the confidence needed to actually then go
in and perform surgery on a modern solid
state radio.
Most of your average hams dont have the
skill or knowledge to do the conversion of
an AA5 which means using some basic RF math too. If you can figure that out,
you
shouldnt have any problems doing it to a
kmart am/fm assuming you have the manual
dexterity to pull coils/rebuild them in such
cramped quarters but then thats what separates those of us who can call
ourselves
radiomen and those who never open and attempt modifications, fixes etc. Never
learn
cw, operate uhf/vhf exclusively and give others here a generally bad time. Oh,
but
they are 'hams'. I proud of the guy for even
comtemplating something like that, more hams
should learn how their radios work and maybe even MAKE one... a direct
conversion, simple superhet, rock bender..
qrp xmtr... all he gets from you guys is 'give up' 'suicide, jimmy'. I meet
so many younger
hams that just dont have a clue and I dont understand how just talking on
vhf/uhf or packet and never actually figuring out or even wondering and
pondering about the
eloquent mathmatics behind it all can give them any pleasure. But then, I
never understood the attraction to CB radio either.
Yep, to me... fun is listening/talking to a far distant HF station on radios
you built/designed
yourself (and maybe even the dipole or yagi)
on a cold star-filled winter's night.
The wonders of the universe around us.
It's interesting, isn't it?
John Kiljan
Years ago I converted an old transistor pocket AM/FM radio to shortwave and it
didn't cost anything more than a bit of time and solder. No new parts were
needed although I wish I had taken the time to put together a band spread
capacitor since the backlash in the main dial got pretty aggravating as I moved
up in frequency.
The reason it was so easy is because on a typical cheap transistor AM radio, the
local oscillator is actually resonated by the ferrite antenna. All I had to do
was start unwinding loops off the the main ferrite slowly till I got it to the
frequency range I wanted. If you go too far, just wind some more back on from
the pile you are going to have all over your workbench. You will be lost, so it
would be nice to have something oscillating at the frequencies that you are
looking to hit as a reference to work toward. I was able to get a settiing that
brought in both the 6 and 9 MHz broadcast bands. (Or, was I just getting the 6
MHz band and its images 910 KHz away? So long ago, I don't remember now.)
Anyway, when you think you have it about right, just cut off the excess wire and
solder the ends of that tiny wire together.
The ferrite antenna will pick up signals of its own, but they will be weak. You
can short over the base of the telescoping FM antenna to a simple two-turn coil
that heads to ground with the two turns wrapped over the far end of the modified
ferrite antenna. That way you can use the FM antenna as the SW antenna and it
also gives you a place to clip on another 10 feet or so of hookup wire that has
an aligator clip soldered to it. To complete the job, I cut and marked up an
index card with the new stations I was hearing (BBC, Deutsche Welle, Havanna,
WWV, R Nederland, etc.) and pasted it over the old dial marker.
Was it any better than a cheap AM/FM/SW radio that I could have found for $5 in
any flea market? Absolutely not! But it was fun and I felt proud of myself
listening to that thing late at night in bed as I drifted of to sleep. To do a
more serious job, in addition to the bandspread I already mentioned, a 455 KHz
loose-coupled local oscillator for sideband and code reception, a
voltage-regulated power supply to the local oscillator, an S-meter readout, and
finally . . . wait for it . . . a digital readout would all be pretty
straightforward if you spread the whole thing out on a breadboard and sank a few
more weekends (and a lot more $'s) into it. But then, that probably wouldn't be
as much fun. And, that's what we're trying to do here isn't it?
Good luck,
-- John (N0BUP)
Brett Hall wrote (quite a few times, it seems):
Graeme Zimmer
> The reason it was so easy is because on a typical cheap transistor AM
radio, the
> local oscillator is actually resonated by the ferrite antenna. All I had
to do
> was start unwinding loops off the the main ferrite slowly till I got it to
the
> frequency range I wanted.
I doubt this very much.
If the ferrite rod winding controls the frequency, then it isn't a superhet,
but some kind of TRF.
If it has an oscillator at all, then it will have a separate oscillator
coil..
73's ........... Zim........... VK3GJZ
Puppin
There is nothing better than do your own radio, turn it on and begin to
listen the bands and discover stations from far away.
I suggest you begin with a simple one, a regenerative, for instance.
There is a kind of magician in listening the shortwave band with a receiver
constructed with a single tube, a phone and half a dozen resistors, capacitors
and coil.
The really beautyful resides in learn, do and see your radio beginnig to
work. And this you can't get "buying" a radio. Do it yourself, wind your
own coils. Begin with simple things. Go step by step increasing
the complexity of your radios, there is no end for it.
You will have time to grow up and compare the more elaborated circuits with
the simplers. The beauty of simple things must be known by the begginer
to take advantage of it or, even to not reinvent the wheel.
Go ahead, modify the coils of an existing receiver make it operate in the
band you want.
Do a converter, use an existing receiver as your first IF, enjoy it.
In the 70s( I was 19) I did a receiver for the 11m band(CB) using an old
receiver with a 455KHz FI, detector and audio without modification. The part
I introduced was a RF amplifier an oscilator and a converter. It gave me
years of pleasure and hundreds of contacts with USA, Canada, Europe, Africa,
Central and South America. Simple and very cheap (all the components came
from old TV selectors and old radios) .
Do it by yourself !
Gilson Puppin - PU5MPL
-----------== Posted via Deja News, The Discussion Network ==----------
http://www.dejanews.com/ Search, Read, Discuss, or Start Your Own
Harry lythall
It's all on my homepages. See the URLs:
http://sm0vpo.8m.com/rx/rxmod.htm - Conversion to any band.
http://sm0vpo.8m.com/rx/160mod.htm - SSB/CW conversion (for 1.8MHz)
Harry