Hi,

Further to my e-mail, having seen the schematic now, it
is probably the antenna which is screwing things up.

Firstly, take the antenna off the collector of the
oscillator and either link-couple it (a couple of turns
with one end grounded) or tap it down the tank coil till
the oscillator starts reliably. You are not looking for an
exact match here but a way of coupling energy more
efficiently into the antenna without the oscillator
thinking that it's his mother.

Secondly, the base biassing you have on the oscillator
is too dependent on individual transistor parameters. I
suggest that you connect the base to ground through another
10K and then adjust the emitter resistor until you have 5
to 10 mA flowing through it. You can tell when you have it
about right by measuring the voltage across it. Touching
the circuit near the coil with your finger should also show
some variation in voltage if the circuit is oscillating.

Finally, you appear to be relying on the battery for an
RF return circuit which is not good. Try placing a
capacitor of about 0.01uF between the supply and ground,
close in to the oscillator.


Cheers - Joe

Joe McElvenney wrote:

Hi,

Further to my e-mail, having seen the schematic now, it
is probably the antenna which is screwing things up.

Firstly, take the antenna off the collector of the
oscillator and either link-couple it (a couple of turns
with one end grounded) or tap it down the tank coil till
the oscillator starts reliably.

Okay, I've not had the experience with this, but my father has. I
normally would ask him for help, but lately, he has been irritated when I
have asked, I suppose because he thinks I already know a lot of these
ideas. Anyway, having used your reply, I was able to get him to explain
what you meant.

In my discussion with him, he mentioned that because of the simplicity of
the radio, I would have what amounts to line loss by link-coupling the
antenna. He suggested the tapping bit. After explaining that to me, I
recall now having seen schematics that used that technique. I think
that's what I'll try.

You are not looking for an exact match here but a way of coupling
energy more efficiently into the antenna without the oscillator thinking
that it's his mother.

If I get the image you're trying to send, I must say that's one effective
way of getting your point across ;-)

Secondly, the base biassing you have on the oscillator
is too dependent on individual transistor parameters. I
suggest that you connect the base to ground through another
10K and then adjust the emitter resistor until you have 5
to 10 mA flowing through it. You can tell when you have it
about right by measuring the voltage across it. Touching
the circuit near the coil with your finger should also show
some variation in voltage if the circuit is oscillating.

Sounds easy enough. I assume you mean the base of Q2?

Finally, you appear to be relying on the battery for an
RF return circuit which is not good. Try placing a
capacitor of about 0.01uF between the supply and ground,
close in to the oscillator.

And this seems to be standard practice, the capacitor. I've seen
reference to that on just about every circuit dealing with oscillators (I
have a small collection of "Engineer's Mini Notebooks" from Radio Snap,
along with a book from an old electronics lab kit I got about 14 years
ago. Shouldn't be a problem to implement.

Cheers - Joe

Thanks for the help, Joe - I'll let you know how it goes when I get the
chance. Right now my father's needing my help loading a trailer with some
carpet and then we're off to our old house to see if the carpet can fit in
anywhere. After that I should have a few hours to tinker, I'll try this
then.

Cheers to you, and 73 de KE4EDD
--
__ ____
/ _| | _ \ Unregistered Linux User #18,000,002
| |__ | _ \
\__/ |___/ Learning is the ONLY substitution for EDUCATION!

Circuit Breaker wrote:

Thanks for the help, Joe - I'll let you know how it goes when I get the
chance. Right now my father's needing my help loading a trailer with

Well, I got the chance.

Worked marvellously. I now have that same 1300 foot range I had before.

Yeah, big deal, I know, but this is big for me - first "properly working",
tunable, hard-soldered FM transmitter for me that can go farther than my
bathroom.

Only problem now is getting rid of the 60-cycle hum from my homebrew power
supply. Should be simple enough, and today I added the missing .1 uF
electrolytic capacitor to the power terminals (was missing, don't know why
I never put it in before). Still have the hum though. That's okay, this
problem should be very well documented in the ARRL handbook. I'll go
consult it.

I plan to revamp my cheesy little freewebs website - I'll be posting the
schematics of things I built and found to be useful. This transmitter
will definitely be among them.

73, de KE4EDD
--
__ ____
/ _| | _ \ Unregistered Linux User #18,000,002
| |__ | _ \
\__/ |___/ Learning is the ONLY substitution for EDUCATION!

On Sat, 03 Jan 2004 01:16:14 -0500, Circuit Breaker
wrote:

Circuit Breaker wrote:

Thanks for the help, Joe - I'll let you know how it goes when I get the
chance. Right now my father's needing my help loading a trailer with

Well, I got the chance.

Worked marvellously. I now have that same 1300 foot range I had before.

Yeah, big deal, I know, but this is big for me - first "properly working",
tunable, hard-soldered FM transmitter for me that can go farther than my
bathroom.

Only problem now is getting rid of the 60-cycle hum from my homebrew power
supply. Should be simple enough, and today I added the missing .1 uF
electrolytic capacitor to the power terminals (was missing, don't know why
I never put it in before). Still have the hum though.

Not surprising. You want something *much* higher in value (a couple of
thousand uF).
--

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

Paul Burridge wrote:

On Sat, 03 Jan 2004 01:16:14 -0500, Circuit Breaker
wrote:

Circuit Breaker wrote:

Thanks for the help, Joe - I'll let you know how it goes when I get the
chance. Right now my father's needing my help loading a trailer with

Well, I got the chance.

Worked marvellously. I now have that same 1300 foot range I had before.

Yeah, big deal, I know, but this is big for me - first "properly working",
tunable, hard-soldered FM transmitter for me that can go farther than my
bathroom.

Only problem now is getting rid of the 60-cycle hum from my homebrew power
supply. Should be simple enough, and today I added the missing .1 uF
electrolytic capacitor to the power terminals (was missing, don't know why
I never put it in before). Still have the hum though.

Not surprising. You want something *much* higher in value (a couple of
thousand uF).

I posted an additional 80 lines or so in reply to this, but whether my ISP
or my newsreader is the device that's screwed up, I don't know. Getting
very irritating though, that every time I spend more than 30 seconds
typing a reply it farhques up.

Anyway...

Between the full-wave bridge rectifier and the regulator is a pair of 35-v
1,000 uF electrolytic cylinders. I considered using a 4,700 uF, but it
only sports a 16v rating (even the pair I have are only 25v). I did put
it in parallel to my radio on the outside of the supply, and it /seemed/
to help some, but I'm tired and didn't take notes. I've played with
different voltages as well, and it seems worse at higher voltages.
Thinking it might be that there is no load on the supply, I added about
300 mW (it's a 450 mW transformer) of a light bulb to the mix. Didn't
help a bit, and really heated the regulator up rather quickly.

I don't expect the circuit to be perfect, in spite of how I "sound" when I
look back over what I've typed. However, I know it's got to be incredibly
simple to fix.

Having forgotten what I typed this morning, and being irritated by how
today has flown right by and I have accomplished close to nothing, I'm
signing off soon and going to bed. Thanks for your suggestions, and I've
got some research to do on the matter this w/e.

73, de KE4EDD

--
__ ____
/ _| | _ \ Unregistered Linux User #18,000,002
| |__ | _ \
\__/ |___/ Learning is the ONLY substitution for EDUCATION!

Paul Burridge wrote:

On Sat, 03 Jan 2004 01:16:14 -0500, Circuit Breaker
wrote:

Circuit Breaker wrote:

Thanks for the help, Joe - I'll let you know how it goes when I get the
chance. Right now my father's needing my help loading a trailer with

Well, I got the chance.

Worked marvellously. I now have that same 1300 foot range I had before.

Yeah, big deal, I know, but this is big for me - first "properly working",
tunable, hard-soldered FM transmitter for me that can go farther than my
bathroom.

Only problem now is getting rid of the 60-cycle hum from my homebrew power
supply. Should be simple enough, and today I added the missing .1 uF
electrolytic capacitor to the power terminals (was missing, don't know why
I never put it in before). Still have the hum though.

Not surprising. You want something *much* higher in value (a couple of
thousand uF).

I posted an additional 80 lines or so in reply to this, but whether my ISP
or my newsreader is the device that's screwed up, I don't know. Getting
very irritating though, that every time I spend more than 30 seconds
typing a reply it farhques up.

Anyway...

Between the full-wave bridge rectifier and the regulator is a pair of 35-v
1,000 uF electrolytic cylinders. I considered using a 4,700 uF, but it
only sports a 16v rating (even the pair I have are only 25v). I did put
it in parallel to my radio on the outside of the supply, and it /seemed/
to help some, but I'm tired and didn't take notes. I've played with
different voltages as well, and it seems worse at higher voltages.
Thinking it might be that there is no load on the supply, I added about
300 mW (it's a 450 mW transformer) of a light bulb to the mix. Didn't
help a bit, and really heated the regulator up rather quickly.

I don't expect the circuit to be perfect, in spite of how I "sound" when I
look back over what I've typed. However, I know it's got to be incredibly
simple to fix.

Having forgotten what I typed this morning, and being irritated by how
today has flown right by and I have accomplished close to nothing, I'm
signing off soon and going to bed. Thanks for your suggestions, and I've
got some research to do on the matter this w/e.

73, de KE4EDD

--
__ ____
/ _| | _ \ Unregistered Linux User #18,000,002
| |__ | _ \
\__/ |___/ Learning is the ONLY substitution for EDUCATION!

On Sat, 03 Jan 2004 01:16:14 -0500, Circuit Breaker
wrote:

Circuit Breaker wrote:

Thanks for the help, Joe - I'll let you know how it goes when I get the
chance. Right now my father's needing my help loading a trailer with

Well, I got the chance.

Worked marvellously. I now have that same 1300 foot range I had before.

Yeah, big deal, I know, but this is big for me - first "properly working",
tunable, hard-soldered FM transmitter for me that can go farther than my
bathroom.

Only problem now is getting rid of the 60-cycle hum from my homebrew power
supply. Should be simple enough, and today I added the missing .1 uF
electrolytic capacitor to the power terminals (was missing, don't know why
I never put it in before). Still have the hum though.

Not surprising. You want something *much* higher in value (a couple of
thousand uF).
--

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

Circuit Breaker wrote:

Thanks for the help, Joe - I'll let you know how it goes when I get the
chance. Right now my father's needing my help loading a trailer with

Well, I got the chance.

Worked marvellously. I now have that same 1300 foot range I had before.

Yeah, big deal, I know, but this is big for me - first "properly working",
tunable, hard-soldered FM transmitter for me that can go farther than my
bathroom.

Only problem now is getting rid of the 60-cycle hum from my homebrew power
supply. Should be simple enough, and today I added the missing .1 uF
electrolytic capacitor to the power terminals (was missing, don't know why
I never put it in before). Still have the hum though. That's okay, this
problem should be very well documented in the ARRL handbook. I'll go
consult it.

I plan to revamp my cheesy little freewebs website - I'll be posting the
schematics of things I built and found to be useful. This transmitter
will definitely be among them.

73, de KE4EDD
--
__ ____
/ _| | _ \ Unregistered Linux User #18,000,002
| |__ | _ \
\__/ |___/ Learning is the ONLY substitution for EDUCATION!

Joe McElvenney wrote:

Hi,

Further to my e-mail, having seen the schematic now, it
is probably the antenna which is screwing things up.

Firstly, take the antenna off the collector of the
oscillator and either link-couple it (a couple of turns
with one end grounded) or tap it down the tank coil till
the oscillator starts reliably.

Okay, I've not had the experience with this, but my father has. I
normally would ask him for help, but lately, he has been irritated when I
have asked, I suppose because he thinks I already know a lot of these
ideas. Anyway, having used your reply, I was able to get him to explain
what you meant.

In my discussion with him, he mentioned that because of the simplicity of
the radio, I would have what amounts to line loss by link-coupling the
antenna. He suggested the tapping bit. After explaining that to me, I
recall now having seen schematics that used that technique. I think
that's what I'll try.

You are not looking for an exact match here but a way of coupling
energy more efficiently into the antenna without the oscillator thinking
that it's his mother.

If I get the image you're trying to send, I must say that's one effective
way of getting your point across ;-)

Secondly, the base biassing you have on the oscillator
is too dependent on individual transistor parameters. I
suggest that you connect the base to ground through another
10K and then adjust the emitter resistor until you have 5
to 10 mA flowing through it. You can tell when you have it
about right by measuring the voltage across it. Touching
the circuit near the coil with your finger should also show
some variation in voltage if the circuit is oscillating.

Sounds easy enough. I assume you mean the base of Q2?

Finally, you appear to be relying on the battery for an
RF return circuit which is not good. Try placing a
capacitor of about 0.01uF between the supply and ground,
close in to the oscillator.

And this seems to be standard practice, the capacitor. I've seen
reference to that on just about every circuit dealing with oscillators (I
have a small collection of "Engineer's Mini Notebooks" from Radio Snap,
along with a book from an old electronics lab kit I got about 14 years
ago. Shouldn't be a problem to implement.

Cheers - Joe

Thanks for the help, Joe - I'll let you know how it goes when I get the
chance. Right now my father's needing my help loading a trailer with some
carpet and then we're off to our old house to see if the carpet can fit in
anywhere. After that I should have a few hours to tinker, I'll try this
then.

Cheers to you, and 73 de KE4EDD
--
__ ____
/ _| | _ \ Unregistered Linux User #18,000,002
| |__ | _ \
\__/ |___/ Learning is the ONLY substitution for EDUCATION!