Topics

SB2 #118 Update

 

Well, got a chance to spend some time on the radio today.

I calibrated the VFO with a good HP counter after letting
both run for about 15 minutes.  I let things cool down,
and repeated and it was still within 1Hz.

I connected a signal generator at just below 7.150 MHz
and could it hear a tone (barely) to about -118 dBm.
I think I heard it lower, but it might have been wishful
thinking.  I was listening to a Baofeng mic up to my ear.

Next was adjusting the bias.  No luck there.  With the
pot turned full counter clockwise I was getting ~115 mA
instead of ~150.  Turning the pot made no difference, but
that gives me something to go on.

So, it could have been a better day, but not bad.

John
W1JDS

ajparent1/kb1gmx
 

Check to be sure you didn't put the zener diode (d1) in backward.

FYI the crystal for the 5351 will age and move in frequency with time
so retest in a month or two. 

Allison

 

The diodes were good.  5.1V supply was good.

I think I cooked my IRF510 somewhere along the line.
No shorts. 
Power out with the modulation pot at it's highest is 5-10 mW.
Bias pot doesn't make any difference to the output despite raising
the gate voltage.  I did start fully CCW.

I think I'm getting a pretty good signal to the gate, but not much
is happening at the output.

I'll replace the IRF510 and try again.

John

On 2/17/2019 8:41 AM, ajparent1/kb1gmx wrote:
Check to be sure you didn't put the zener diode (d1) in backward.

FYI the crystal for the 5351 will age and move in frequency with time
so retest in a month or two. 

Allison

Steven Weber
 

It’s kind of hard to cook those fets. If it’s not shorted, it’s probably good.

It would take a pretty good static spike to cook the gate.

 

Do you have 12V on the tab?

Your not seeing any current increase with the bias pot?

You sure the voltage is making it to the gate?

 

Take  a close look at T1 and T2 and make sure their installed correctly.

Transpose the ends of the windings and it doesn’t work anymore.

 

Just going down the check list. This is when having a ‘Scope saves a lot of time.

KD1JV

 

The diodes were good.  5.1V supply was good.

I think I cooked my IRF510 somewhere along the line.
No shorts. 
Power out with the modulation pot at it's highest is 5-10 mW.
Bias pot doesn't make any difference to the output despite raising
the gate voltage.  I did start fully CCW.

I think I'm getting a pretty good signal to the gate, but not much
is happening at the output.

I'll replace the IRF510 and try again.

John


On 2/17/2019 8:41 AM, ajparent1/kb1gmx wrote:

Check to be sure you didn't put the zener diode (d1) in backward.

FYI the crystal for the 5351 will age and move in frequency with time
so retest in a month or two. 

Allison

 

 

 

You know, a picture's worth 1000 words, or approximately one awshit.

I did have to replace the IRF510, but only to the other side of the PCB.
That's what I get for building past midnight...

I'll tweak it at the office and see what it looks like on the SA.
I did see the my power meter peaking up to around 4W just
playing around a bit.

Where's the best place to check the modulation with a scope?
At the gate of the IRF510 or the antenna?

Thanks for your patience!

John

On 2/18/2019 8:06 PM, Steven Weber wrote:

It’s kind of hard to cook those fets. If it’s not shorted, it’s probably good.

It would take a pretty good static spike to cook the gate.

 

Do you have 12V on the tab?

Your not seeing any current increase with the bias pot?

You sure the voltage is making it to the gate?

 

Take  a close look at T1 and T2 and make sure their installed correctly.

Transpose the ends of the windings and it doesn’t work anymore.

 

Just going down the check list. This is when having a ‘Scope saves a lot of time.

KD1JV

 

The diodes were good.  5.1V supply was good.

I think I cooked my IRF510 somewhere along the line.
No shorts. 
Power out with the modulation pot at it's highest is 5-10 mW.
Bias pot doesn't make any difference to the output despite raising
the gate voltage.  I did start fully CCW.

I think I'm getting a pretty good signal to the gate, but not much
is happening at the output.

I'll replace the IRF510 and try again.

John

On 2/17/2019 8:41 AM, ajparent1/kb1gmx wrote:

Check to be sure you didn't put the zener diode (d1) in backward.

FYI the crystal for the 5351 will age and move in frequency with time
so retest in a month or two. 

Allison

 

 


Steven Weber
 

I guess putting it on the wrong side of the board would make it not work so good, hi.

Surprised that didn’t hurt it.

Glad your on the right track now.

KD1JV

 

 

You know, a picture's worth 1000 words, or approximately one awshit.

I did have to replace the IRF510, but only to the other side of the PCB.
That's what I get for building past midnight...

I'll tweak it at the office and see what it looks like on the SA.
I did see the my power meter peaking up to around 4W just
playing around a bit.

Where's the best place to check the modulation with a scope?
At the gate of the IRF510 or the antenna?

Thanks for your patience!

John


On 2/18/2019 8:06 PM, Steven Weber wrote:

It’s kind of hard to cook those fets. If it’s not shorted, it’s probably good.

It would take a pretty good static spike to cook the gate.

 

Do you have 12V on the tab?

Your not seeing any current increase with the bias pot?

You sure the voltage is making it to the gate?

 

Take  a close look at T1 and T2 and make sure their installed correctly.

Transpose the ends of the windings and it doesn’t work anymore.

 

Just going down the check list. This is when having a ‘Scope saves a lot of time.

KD1JV

 

The diodes were good.  5.1V supply was good.

I think I cooked my IRF510 somewhere along the line.
No shorts. 
Power out with the modulation pot at it's highest is 5-10 mW.
Bias pot doesn't make any difference to the output despite raising
the gate voltage.  I did start fully CCW.

I think I'm getting a pretty good signal to the gate, but not much
is happening at the output.

I'll replace the IRF510 and try again.

John

On 2/17/2019 8:41 AM, ajparent1/kb1gmx wrote:

Check to be sure you didn't put the zener diode (d1) in backward.

FYI the crystal for the 5351 will age and move in frequency with time
so retest in a month or two. 

Allison

 

 

 

 

 

I had a few minutes on the SA today.  Not quite the power I was expecting, but the
separation is great!

For reference, the current with the bias pot turned CCW was about 118 mA.
I raised it 30 mA to about 150.  I'll try to raise it to 180mA and try again
in a few days.

   

On 2/19/2019 7:09 AM, Steven Weber wrote:

I guess putting it on the wrong side of the board would make it not work so good, hi.

Surprised that didn’t hurt it.

Glad your on the right track now.

KD1JV

 

 

You know, a picture's worth 1000 words, or approximately one awshit.

I did have to replace the IRF510, but only to the other side of the PCB.
That's what I get for building past midnight...

I'll tweak it at the office and see what it looks like on the SA.
I did see the my power meter peaking up to around 4W just
playing around a bit.

Where's the best place to check the modulation with a scope?
At the gate of the IRF510 or the antenna?

Thanks for your patience!


 

Got some time on the spectrum analyzer over the weekend.
I measured power in CW mode.

I think I bumped the MOD adjustment so I'll have to redo that sometime this week.




On 2/19/2019 7:09 AM, Steven Weber wrote:

I guess putting it on the wrong side of the board would make it not work so good, hi.

Surprised that didn’t hurt it.

Glad your on the right track now.

KD1JV

 

 

You know, a picture's worth 1000 words, or approximately one awshit.

I did have to replace the IRF510, but only to the other side of the PCB.
That's what I get for building past midnight...

I'll tweak it at the office and see what it looks like on the SA.
I did see the my power meter peaking up to around 4W just
playing around a bit.

Where's the best place to check the modulation with a scope?
At the gate of the IRF510 or the antenna?

Thanks for your patience!

John

On 2/18/2019 8:06 PM, Steven Weber wrote:

It’s kind of hard to cook those fets. If it’s not shorted, it’s probably good.

It would take a pretty good static spike to cook the gate.

 

Do you have 12V on the tab?

Your not seeing any current increase with the bias pot?

You sure the voltage is making it to the gate?

 

Take  a close look at T1 and T2 and make sure their installed correctly.

Transpose the ends of the windings and it doesn’t work anymore.

 

Just going down the check list. This is when having a ‘Scope saves a lot of time.

KD1JV

 

The diodes were good.  5.1V supply was good.

I think I cooked my IRF510 somewhere along the line.
No shorts. 
Power out with the modulation pot at it's highest is 5-10 mW.
Bias pot doesn't make any difference to the output despite raising
the gate voltage.  I did start fully CCW.

I think I'm getting a pretty good signal to the gate, but not much
is happening at the output.

I'll replace the IRF510 and try again.

John

On 2/17/2019 8:41 AM, ajparent1/kb1gmx wrote:

Check to be sure you didn't put the zener diode (d1) in backward.

FYI the crystal for the 5351 will age and move in frequency with time
so retest in a month or two. 

Allison