On Sun, 27 Jul 2003 22:33:48 +0100, Paul Burridge
wrote:


How did you go with Win's soft start motor controller?

Currently under construction...
--

Hello Paul,
you are dragging the anchor a bit. That was months ago! :-)

Have a look here
http://www.ife.tugraz.at/datashts/nsc/h7912.pdf
Page 9. Application hints, has some good reading
on how to play around with the input transformer.

Is Henry's Radio still around? They used sell
sets of IF coils for hobbyists and experimenters. My
Henry's catalogue is a bit old. A nice Indian gent in
an electronics junk shop in Edgeware Road gave it
to me in 1973. I should come over there and get
a more up to date copy. Are the electronic disposal
shops still there?
Maybe rob some 455 KHz IF coils out of a dud
transistor radio if necessary. Save some dosh.

Get that Dalo etch resist pen out, bottle of ferric chloride
and sharpen your old soldering iron.

You have a good Tek CRO and a Signal Generator.

Do I sound like I am pushing you? Heh heh heh....

Regards,
John Crighton
Sydney

Back to your interference problem. Is your operating
channel frequency smack in the middle of the 40 Mhz band?
If so, maybe you could try a different set of crystals, so
that you operate as far away from everyone else as
possible. Or simply just borrow a different set of crystals
in case there is a weird mix going on, just to eliminate
that possibility.

We've recently got wise to that one and I've ordered a pair of xtals
from the *last* channel of the band. That's what we'll be running with
come the last week in August, when we're due up for the next filming.


Not necessarily the solution, I got bitten by that one once some 9 or 10
years ago when I used to fly radio controlled aircraft (in the UK on 35MHz).
It bothered me when someone else at the flying field had the same crystal as
I did and I had to wait for them to finish flying before I could fly. So
bought another pair of crystals, the highest I could find, if I recall that
was channel 83 (35.230MHz). Everything was fine for a while but a few weeks
later I crashed after losing radio contact with my plane.

A little investigation (in between gluing the aircraft bits back together)
found the cause. A channel vs frequency listing, compared with the MHz
printed on the crystal case revealed that the receivers were single
conversion superhets with 110KHz IF. Channel separation was 10KHz. Clearly
with that setup, image rejection is practically negligible. So someone
transmitting on channel 61, 220KHz away, interferes with channel 83. After
that I went back to my crystals on 76 smack in the middle of everyone elses,
learnt to be patient if someone was already using the channel, and had no
more problems ;-)

Hans G0UPL
http://www.HansSummers.com

Back to your interference problem. Is your operating
channel frequency smack in the middle of the 40 Mhz band?
If so, maybe you could try a different set of crystals, so
that you operate as far away from everyone else as
possible. Or simply just borrow a different set of crystals
in case there is a weird mix going on, just to eliminate
that possibility.

We've recently got wise to that one and I've ordered a pair of xtals
from the *last* channel of the band. That's what we'll be running with
come the last week in August, when we're due up for the next filming.


Not necessarily the solution, I got bitten by that one once some 9 or 10
years ago when I used to fly radio controlled aircraft (in the UK on 35MHz).
It bothered me when someone else at the flying field had the same crystal as
I did and I had to wait for them to finish flying before I could fly. So
bought another pair of crystals, the highest I could find, if I recall that
was channel 83 (35.230MHz). Everything was fine for a while but a few weeks
later I crashed after losing radio contact with my plane.

A little investigation (in between gluing the aircraft bits back together)
found the cause. A channel vs frequency listing, compared with the MHz
printed on the crystal case revealed that the receivers were single
conversion superhets with 110KHz IF. Channel separation was 10KHz. Clearly
with that setup, image rejection is practically negligible. So someone
transmitting on channel 61, 220KHz away, interferes with channel 83. After
that I went back to my crystals on 76 smack in the middle of everyone elses,
learnt to be patient if someone was already using the channel, and had no
more problems ;-)

Hans G0UPL
http://www.HansSummers.com

On 28 Jul 2003 07:13:56 GMT, (Michael Black)
wrote:

John Crighton ) writes:
Maybe rob some 455 KHz IF coils out of a dud
transistor radio if necessary. Save some dosh.

It would be interesting to have some tests done on the original
receiver. If I remember the start of the thread, the receiver
is not sensitive enough. I can't help but wonder if it's insensitive
or it's too sensitive, leading to overload in the front end.
That would be just as bad (in terms of operational range) as an insensitive
receiver.

Likewise, if one had an idea of the IF bandwidth, it would be easier
to know if the problem really needs fixing, or there is some other
issue. If the thing is using some sort of ceramic filter, looking
at the board would hopefully say what type (unless the markings have
been sanded off), and then the specs could be found. Assuming it's
a standard IF frequency, maybe one could find a narrower filter
that would drop right in. For all we know, it may have too wide
an IF, and that's causing the initial problem.

Knowing the bandwidth of the existing filter would also make it
easier to figure out a complete replacement for the receiver.
In this day and age, ceramic or crystal filters are the way to go,
not a bunch of IF transformers. Pull parts out of a cordless phone,
at least the 49MHz type, and you'll get a filter suitable for
narrow deviation FM and a crystal for converting from 10.7MHz
to 455KHz. If FM happens to be the operating mode, then pull
out the whole IF strip. If that filter is too wide, pull the
455KHz ceramic filter out of a am BCB radio, or for something
narrower, a CB set. The possibilities are endless.

Michael VE2BVW


Hello Michael,
you are correct, there are many possibilities. I would
like him to do some tests also.

The main stumbling block for Paul is no information
on the present Sanwa receiver and an understandable
reluctance to poke around and then kill it
accidentally, especially if it is borrowed or belongs
to a mate.

I suggested building a new Rx that is physically big
so that experiments and mods are easily done by
Paul. If the CRO probe slips.....no big deal. :-)

We know of this LM1872
http://www.ife.tugraz.at/datashts/nsc/h7912.pdf
that we can all look at and help out with suggestions.
Do you know of anything else we can all see on a
website?

Regards,
John Crighton
Sydney

On 28 Jul 2003 07:13:56 GMT, (Michael Black)
wrote:

John Crighton ) writes:
Maybe rob some 455 KHz IF coils out of a dud
transistor radio if necessary. Save some dosh.

It would be interesting to have some tests done on the original
receiver. If I remember the start of the thread, the receiver
is not sensitive enough. I can't help but wonder if it's insensitive
or it's too sensitive, leading to overload in the front end.
That would be just as bad (in terms of operational range) as an insensitive
receiver.

Likewise, if one had an idea of the IF bandwidth, it would be easier
to know if the problem really needs fixing, or there is some other
issue. If the thing is using some sort of ceramic filter, looking
at the board would hopefully say what type (unless the markings have
been sanded off), and then the specs could be found. Assuming it's
a standard IF frequency, maybe one could find a narrower filter
that would drop right in. For all we know, it may have too wide
an IF, and that's causing the initial problem.

Knowing the bandwidth of the existing filter would also make it
easier to figure out a complete replacement for the receiver.
In this day and age, ceramic or crystal filters are the way to go,
not a bunch of IF transformers. Pull parts out of a cordless phone,
at least the 49MHz type, and you'll get a filter suitable for
narrow deviation FM and a crystal for converting from 10.7MHz
to 455KHz. If FM happens to be the operating mode, then pull
out the whole IF strip. If that filter is too wide, pull the
455KHz ceramic filter out of a am BCB radio, or for something
narrower, a CB set. The possibilities are endless.

Michael VE2BVW


Hello Michael,
you are correct, there are many possibilities. I would
like him to do some tests also.

The main stumbling block for Paul is no information
on the present Sanwa receiver and an understandable
reluctance to poke around and then kill it
accidentally, especially if it is borrowed or belongs
to a mate.

I suggested building a new Rx that is physically big
so that experiments and mods are easily done by
Paul. If the CRO probe slips.....no big deal. :-)

We know of this LM1872
http://www.ife.tugraz.at/datashts/nsc/h7912.pdf
that we can all look at and help out with suggestions.
Do you know of anything else we can all see on a
website?

Regards,
John Crighton
Sydney

On Mon, 28 Jul 2003 10:19:13 +0100, "Hans Summers"
wrote:


Back to your interference problem. Is your operating
channel frequency smack in the middle of the 40 Mhz band?
If so, maybe you could try a different set of crystals, so
that you operate as far away from everyone else as
possible. Or simply just borrow a different set of crystals
in case there is a weird mix going on, just to eliminate
that possibility.

We've recently got wise to that one and I've ordered a pair of xtals
from the *last* channel of the band. That's what we'll be running with
come the last week in August, when we're due up for the next filming.


Not necessarily the solution, I got bitten by that one once some 9 or 10
years ago when I used to fly radio controlled aircraft (in the UK on 35MHz).
It bothered me when someone else at the flying field had the same crystal as
I did and I had to wait for them to finish flying before I could fly. So
bought another pair of crystals, the highest I could find, if I recall that
was channel 83 (35.230MHz). Everything was fine for a while but a few weeks
later I crashed after losing radio contact with my plane.

A little investigation (in between gluing the aircraft bits back together)
found the cause. A channel vs frequency listing, compared with the MHz
printed on the crystal case revealed that the receivers were single
conversion superhets with 110KHz IF. Channel separation was 10KHz. Clearly
with that setup, image rejection is practically negligible. So someone
transmitting on channel 61, 220KHz away, interferes with channel 83. After
that I went back to my crystals on 76 smack in the middle of everyone elses,
learnt to be patient if someone was already using the channel, and had no
more problems ;-)

Hans G0UPL
http://www.HansSummers.com


Hello Hans,
what brand/make was that R/C set that you had?

You have reminded me of a silly incident at my model
flying club decades ago. One of the wealthier club
members was having all sorts of trouble with his
model, engine and radio gear so he flung heaps of
money at a ready made, ready to fly model with an
expensive four stroke engine, and a new expensive
all singing and dancing radio control set. First day
out with the new model and everything is going well
for him, he was doing stunts all over the sky.

My models were el cheapo sticks and tissue construction,
I couldn't afford nice covering film/material. I was
more interested in home built radio control gear. Radio
assisted free flight was more my style.
When the fuel ran out in my models I didn't mind
walking a few hundred yards if necessary to retrieve
my model. So I am off for a long walk with my transmitter
still switched on as one would. (The receiver gets
switched off first then the transmitter.)

The rich guy is stunting around and decides to buzz
me at low level about 20 feet above the ground.
His model flies over me and then nose dives into
the ground near by. I could here his servos twitching
away as I walked past the wreckage.
After I retrieved my model and switched off my
transmitter, I stopped by the little gathering at the
wreck site. The rich guy was operating his servos OK
and scratching his head. " I spend thousands on
my model and that ******* John Crighton comes
here every weekend with 50 dollars worth of homebuilt
junk and flies. It just isn't fair." "Moan...grumble..moan."
I didn't try to explain that his receiver got swamped. His
mates put the crash down to pilot error at low level, and
that was that.

Fun and games, eh! :-)
Regards,
John Crighton
Sydney

On Mon, 28 Jul 2003 10:19:13 +0100, "Hans Summers"
wrote:


Back to your interference problem. Is your operating
channel frequency smack in the middle of the 40 Mhz band?
If so, maybe you could try a different set of crystals, so
that you operate as far away from everyone else as
possible. Or simply just borrow a different set of crystals
in case there is a weird mix going on, just to eliminate
that possibility.

We've recently got wise to that one and I've ordered a pair of xtals
from the *last* channel of the band. That's what we'll be running with
come the last week in August, when we're due up for the next filming.


Not necessarily the solution, I got bitten by that one once some 9 or 10
years ago when I used to fly radio controlled aircraft (in the UK on 35MHz).
It bothered me when someone else at the flying field had the same crystal as
I did and I had to wait for them to finish flying before I could fly. So
bought another pair of crystals, the highest I could find, if I recall that
was channel 83 (35.230MHz). Everything was fine for a while but a few weeks
later I crashed after losing radio contact with my plane.

A little investigation (in between gluing the aircraft bits back together)
found the cause. A channel vs frequency listing, compared with the MHz
printed on the crystal case revealed that the receivers were single
conversion superhets with 110KHz IF. Channel separation was 10KHz. Clearly
with that setup, image rejection is practically negligible. So someone
transmitting on channel 61, 220KHz away, interferes with channel 83. After
that I went back to my crystals on 76 smack in the middle of everyone elses,
learnt to be patient if someone was already using the channel, and had no
more problems ;-)

Hans G0UPL
http://www.HansSummers.com


Hello Hans,
what brand/make was that R/C set that you had?

You have reminded me of a silly incident at my model
flying club decades ago. One of the wealthier club
members was having all sorts of trouble with his
model, engine and radio gear so he flung heaps of
money at a ready made, ready to fly model with an
expensive four stroke engine, and a new expensive
all singing and dancing radio control set. First day
out with the new model and everything is going well
for him, he was doing stunts all over the sky.

My models were el cheapo sticks and tissue construction,
I couldn't afford nice covering film/material. I was
more interested in home built radio control gear. Radio
assisted free flight was more my style.
When the fuel ran out in my models I didn't mind
walking a few hundred yards if necessary to retrieve
my model. So I am off for a long walk with my transmitter
still switched on as one would. (The receiver gets
switched off first then the transmitter.)

The rich guy is stunting around and decides to buzz
me at low level about 20 feet above the ground.
His model flies over me and then nose dives into
the ground near by. I could here his servos twitching
away as I walked past the wreckage.
After I retrieved my model and switched off my
transmitter, I stopped by the little gathering at the
wreck site. The rich guy was operating his servos OK
and scratching his head. " I spend thousands on
my model and that ******* John Crighton comes
here every weekend with 50 dollars worth of homebuilt
junk and flies. It just isn't fair." "Moan...grumble..moan."
I didn't try to explain that his receiver got swamped. His
mates put the crash down to pilot error at low level, and
that was that.

Fun and games, eh! :-)
Regards,
John Crighton
Sydney

On Mon, 28 Jul 2003 13:20:27 GMT, (John Crighton)
wrote:

The rich guy is stunting around and decides to buzz
me at low level about 20 feet above the ground.
His model flies over me and then nose dives into
the ground near by. I could here his servos twitching
away as I walked past the wreckage.
After I retrieved my model and switched off my
transmitter, I stopped by the little gathering at the
wreck site. The rich guy was operating his servos OK
and scratching his head. " I spend thousands on
my model and that ******* John Crighton comes
here every weekend with 50 dollars worth of homebuilt
junk and flies. It just isn't fair." "Moan...grumble..moan."
I didn't try to explain that his receiver got swamped. His
mates put the crash down to pilot error at low level, and
that was that.

John, what in your experience causes this 'servo-twitching'? I've
observed it myself at close hand many times. The last time it
happened, we cured it by isolating the die-cast box the rx was mounted
in from the chassis. I still can't figure out why this worked, as I'd
have thought grounding it *ought* to solve the problem. But in this
instance, grounding it *created* the problem and isolating it solved
it! Sometimes when I see those servos behaving like they've got a mind
of their own it almost makes me believe in the supernatural.
--

"I believe history will be kind to me, since I intend
to write it." - Winston Churchill

On Mon, 28 Jul 2003 13:20:27 GMT, (John Crighton)
wrote:

The rich guy is stunting around and decides to buzz
me at low level about 20 feet above the ground.
His model flies over me and then nose dives into
the ground near by. I could here his servos twitching
away as I walked past the wreckage.
After I retrieved my model and switched off my
transmitter, I stopped by the little gathering at the
wreck site. The rich guy was operating his servos OK
and scratching his head. " I spend thousands on
my model and that ******* John Crighton comes
here every weekend with 50 dollars worth of homebuilt
junk and flies. It just isn't fair." "Moan...grumble..moan."
I didn't try to explain that his receiver got swamped. His
mates put the crash down to pilot error at low level, and
that was that.

John, what in your experience causes this 'servo-twitching'? I've
observed it myself at close hand many times. The last time it
happened, we cured it by isolating the die-cast box the rx was mounted
in from the chassis. I still can't figure out why this worked, as I'd
have thought grounding it *ought* to solve the problem. But in this
instance, grounding it *created* the problem and isolating it solved
it! Sometimes when I see those servos behaving like they've got a mind
of their own it almost makes me believe in the supernatural.
--

"I believe history will be kind to me, since I intend
to write it." - Winston Churchill

On Mon, 28 Jul 2003 07:02:53 GMT, (John Crighton)
wrote:

On Sun, 27 Jul 2003 22:33:48 +0100, Paul Burridge
wrote:


How did you go with Win's soft start motor controller?

Currently under construction...
--

Hello Paul,
you are dragging the anchor a bit. That was months ago! :-)

Have a look here
http://www.ife.tugraz.at/datashts/nsc/h7912.pdf

You'll have to forgive me here, John, as i'm battling with a duff
display on the computer I'm using at the moment and I was only able to
glimpse the data for a few seconds, but this chip doesn't seem to be
suitable for 40Mhz FM, does it? I'm sure your general solution to the
problem is an excellent one, though, if a suitable chip can be found.
--

"I believe history will be kind to me, since I intend
to write it." - Winston Churchill