Runboard.com
You're welcome.
Community logo


runboard.com       Sign up (learn about it) | Sign in (lost password?)


Page:  1  2 

 
andybristol Profile
Live feed
Blog
Friends
Miscellaneous info


Global user

Registered: 11-2010
Posts: 26
Karma: 0 (+0/-0)
Reply | Quote
KL400 strangeness


I've recently got an RM KL400, which for transmit works great, but getting some strange effects on receive.

Even on AM, after ending transmission the receive is initially weak, gradually fading back over about the next 10 seconds.

I've tried it on multiple radios with the same result.

I can get around it by quickly turning off the amp then quickly keying the mic, receive is then back to 100%. But i cant see me being patient enough to do that on every single over!

Anyone else had something similar or maybe be able to explain this ?

Thanks,

Andy 26FB400
5/Feb/2011, 1:48 pm Link to this post Send Email to andybristol   Send PM to andybristol Blog
 
Hot Fusion Profile
Live feed
Blog
Friends
Miscellaneous info

Management
Global user

Registered: 03-2008
Location: South West England
Posts: 1372
Karma: 7 (+7/-0)
Reply | Quote
Re: KL400 strangeness


It sounds like an RF spike entering the rig when going back to receive causing the AGC to wind back, just as it would on a very strong signal.

Quite what it is with the '400 that is causing this I don't know - maybe one of the others on here will have some ideas.

---
Andy - 26 FB107
5/Feb/2011, 2:13 pm Link to this post Send Email to Hot Fusion   Send PM to Hot Fusion
 
andybristol Profile
Live feed
Blog
Friends
Miscellaneous info


Global user

Registered: 11-2010
Posts: 26
Karma: 0 (+0/-0)
Reply | Quote
Re: KL400 strangeness


Ahhh, thats interesting, hadnt thought of that at all. Perhaps thats why its happy when switching back to receive when NOT using the linear. Radios in question are magnum delta force and crt ss3900.

Thanks.
5/Feb/2011, 2:28 pm Link to this post Send Email to andybristol   Send PM to andybristol Blog
 
YT2095 Profile
Live feed
Blog
Friends
Miscellaneous info

Freebander
Global user

Registered: 12-2010
Location: the Black Country
Posts: 188
Karma: 1 (+1/-0)
Reply | Quote
Re: KL400 strangeness


yes AGC is the 1`st thought here also, I would think that the switch-over relay isn`t responding at the correct time for the RX/TX changeover.

some can self oscillate for a short while afterwards.




---
I`m also on Twitter as "YT2095" ;)
5/Feb/2011, 9:44 pm Link to this post Send Email to YT2095   Send PM to YT2095 Blog
 
andybristol Profile
Live feed
Blog
Friends
Miscellaneous info


Global user

Registered: 11-2010
Posts: 26
Karma: 0 (+0/-0)
Reply | Quote
Re: KL400 strangeness


I've been doing some experiments like turning off the linear before i let go of the mic, all adding weight to the AGC theory.

I've been looking for a new project so might build something to leave the rig on TX for a fraction of a second after turning off the linear.

I've found various mods to allow manual control of the KL500, looking at the diagram the 400 seems very similar.

Thanks guys,

Andy
6/Feb/2011, 11:09 am Link to this post Send Email to andybristol   Send PM to andybristol Blog
 
YT2095 Profile
Live feed
Blog
Friends
Miscellaneous info

Freebander
Global user

Registered: 12-2010
Location: the Black Country
Posts: 188
Karma: 1 (+1/-0)
Reply | Quote
Re: KL400 strangeness


take a look here: [sign in to see URL]%[sign in to see URL]
and scroll down to self-oscillation, it may give you an idea of what to check out.

I had an el-cheapo 25w linear way back in the old CB days, I think it was a Moonraker or something like that, and this thing was Crazy!
I could key up for a sec, and then disconnect the patch lead from the rig and the thing would carry on transmitting regardless as long as there was power to it!
of course it`s TX freq was all over the place spewing harmonics galore, when operating this way, it burned itself out eventually as I was fascinated by this phenomenon emoticon

you probably need some sort of damping or adjusting the gate voltage?

have you tried putting a field strength meter by your antenna and watching what happens after you de-key?
an in-line power meter between the ant and the linear would be just as good.

see if there`s a lag?


---
I`m also on Twitter as "YT2095" ;)
6/Feb/2011, 11:42 am Link to this post Send Email to YT2095   Send PM to YT2095 Blog
 
andybristol Profile
Live feed
Blog
Friends
Miscellaneous info


Global user

Registered: 11-2010
Posts: 26
Karma: 0 (+0/-0)
Reply | Quote
Re: KL400 strangeness


Its switches off ok from what I can tell (i see your point though, this oscillation may be happening in a too tiny to observe, but big enough time frame to cause a problem). I'll certainly try the power meter test, might be too slow to see any spike thats there though.

Will report back on that one.

Thanks again - lots to think about !
6/Feb/2011, 12:02 pm Link to this post Send Email to andybristol   Send PM to andybristol Blog
 
andybristol Profile
Live feed
Blog
Friends
Miscellaneous info


Global user

Registered: 11-2010
Posts: 26
Karma: 0 (+0/-0)
Reply | Quote
Re: KL400 strangeness


Cant see anything significant with the power meter, but i suspect its simply too slow to see anything anyway.

Can I be a bit cheeky ? Since you are clearly quite hot on your electronics can you have a quick look at the schematic for me ?

[sign in to see URL]

Basically, I've found one reference online to the fact that newer KL500s can be manually switched using pins 3 & 4 of the service connector. Looking at the schematic it does seem to connect near the RF detection circuitry.

The theory being that the RF detection gets disconnected, and I can then switch the amp to TX myself with an external relay.

My backup plan is to use a relay connected to the ON/OFF switch to cut the AMP.
6/Feb/2011, 12:20 pm Link to this post Send Email to andybristol   Send PM to andybristol Blog
 
andybristol Profile
Live feed
Blog
Friends
Miscellaneous info


Global user

Registered: 11-2010
Posts: 26
Karma: 0 (+0/-0)
Reply | Quote
Re: KL400 strangeness


Looking inside - i've found a capacitor (C21) is broken in half. This is a new unit, so must have left the factory like that.

I have no idea if this is the cause of my troubles or not, will replace and report back!

Andy
6/Feb/2011, 2:17 pm Link to this post Send Email to andybristol   Send PM to andybristol Blog
 
andybristol Profile
Live feed
Blog
Friends
Miscellaneous info


Global user

Registered: 11-2010
Posts: 26
Karma: 0 (+0/-0)
Reply | Quote
Re: KL400 strangeness


Ok - having done a great deal of fiddling, i'm sure its NOT the burner upsetting AGC.

Short version, I have modified the burner for external control from a relay box. However, simply cutting the amp TX early (about [sign in to see URL] before returning radio to RX) was not enough.

How I have sorted this is to also link the other pole of the relay to cut the ON/OFF control too. It seems that completely turning off the amp is what is required, as opposed to killing tx mode.

It was a pain in the neck, but all works lovely now - even better I dont have to use the SSB setting on the burner any more!

If anyone wants to know how to manually control these amps let me know. I'll probably stick schematics on here at some point.
14/Feb/2011, 12:35 pm Link to this post Send Email to andybristol   Send PM to andybristol Blog
 


Add a reply

Page:  1  2 





You are not logged in (login)