Elecraft : K2 SSB audio quality

[Martin.Evans-2]

Hello, I've recently started to use my K2/KPA100 on SSB running 100W
with an MH2 mike mostly on 80m. I use 2:1 compression and mic preamp is
set to 2. The antenna is an 120ft doublet, 30ft of 300ohm ribbon feeder,
remote mounted z match tuner right under the centre of the doublet and
approx 70ft RG58 coax to the rig. I have no RF earth but neither do I
get much RFI in the house. One end of the antenna is about 10m above the
operating position and I'm on the ground floor. I've had varying reports
on the audio quality. Here are a few things I have done/found:
 
Every now and then I would get a high current message after which my RF
peaks (as shown on the K2 bargraph) would drop right down. My remote
mounted z match tuner uses old broadcast receiver variable caps and I
think one of them might have been flashing on speech peaks. I have
backed off the power to 90W and it seems a lot better. The funny thing
is that when I run at 100W on CW I don't have any probs (ie no high
current messages). Is there something about the RF peaks on SSB, do they
overshoot sometimes or is it something to do with rate of rise of the RF
voltage?
 
When I first start an over on SSB the bargraph follows the speech
waveform and is what I could call "lively" but sometimes it goes very
sluggish and doesn't seem to be following the audio, is this normal.
Sometimes the bargraph seems to disappear altogether.
 
The antenna and tuner are balanced and I've added a choke balun and
various ferrites (inc 3 turns on the mic lead and 4 turns on the power
supply lead) to keep any RF off the rig chassis. I hold the mic about 4
inches away since I thought I might be overdriving the audio.
 
I did have reports of sounding like I was speaking through a kazoo but I
think I may have fixed that by moving the power supply (linear one with
big toroidal tx) a bit further away from the rig.
 
Some guys report that it sounds a bit scratchy.
 
I have checked the KPA100 biasing and it is spot on with the manual and
also the carrier suppression.
 
Unfortunately I don't have another rig to monitor my signal. I do have a
30Meg scope.
 
I don't think the audio is bad but perhaps not the best I could get out
of the K2. Are there any tests/mods/tricks I could try??

Costain Group PLC, Registration Nos.: 1393773
Costain Ltd, Registration Nos.: 00610201
Costain Building & Civil Engineering Ltd, Registration Nos.: 01054232
Costain Engineering & Construction Ltd, Registration Nos.: 02440829
Costain Engineering & Construction (Overseas) Ltd, Registration Nos.: 02440830
Costain Oil, Gas & Process Ltd, Registration Nos.: 00786418
 
Registered Office: Costain House, Vanwall Business Park, Maidenhead, Berkshire, SL6 4UB.
 
The information contained in this e-mail is confidential and may be privileged. If you are not the intended recipient you must not copy, distribute or otherwise disclose its contents. If you have received this e-mail in error please notify us immediately and then delete the message.
Please visit www.costain.com  Before you print think about the ENVIRONMENT
This message has been checked for all email viruses by the NetscanCentral solution.
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

[Don Wilhelm-4]

Martin,

You may be driving the internal ALC too hard.  With the MH2 mike, it is
rare to have to use SSBA higher than 1.  Try bumping up the compression
to 3, I think you will like it better.

A HiCur message only relates to the base K2, not the KPA100, and means
the current set in CAL CUR is being exceeded.  Make certain CAL CUR is
set to 3.50 and if the HiCur messages persist, check the windings of T4
and the LPF in the base K2 for any problems.
Of course, the LPF of the KPA100 is also in-line, so there could be a
possibility of a problem in that LPF too.
If it is a LPF problem, the HiCur problem will only occur on one or two
bands.  If it is on all bands, look to the power supply and the cable(s)
and connectors.  Everything should be tight.  On SSB, the instantaneous
current change can be higher than with CW and if there is too much
resistance in the power supply system, the voltage could drop for an
instant and create a HiCur situation.

If you are setting the power control to "full right" instead of 100
watts, that could also be the cause of the occasional HiCur messages and
power overshoot.  In the full right position, there is not as much
control headroom, the K2 is trying to drive "flat out".

73,
Don W3FPR

[hidden email] wrote:

> Hello, I've recently started to use my K2/KPA100 on SSB running 100W
> with an MH2 mike mostly on 80m. I use 2:1 compression and mic preamp is
> set to 2. The antenna is an 120ft doublet, 30ft of 300ohm ribbon feeder,
> remote mounted z match tuner right under the centre of the doublet and
> approx 70ft RG58 coax to the rig. I have no RF earth but neither do I
> get much RFI in the house. One end of the antenna is about 10m above the
> operating position and I'm on the ground floor. I've had varying reports
> on the audio quality. Here are a few things I have done/found:
>  
> Every now and then I would get a high current message after which my RF
> peaks (as shown on the K2 bargraph) would drop right down. My remote
> mounted z match tuner uses old broadcast receiver variable caps and I
> think one of them might have been flashing on speech peaks. I have
> backed off the power to 90W and it seems a lot better. The funny thing
> is that when I run at 100W on CW I don't have any probs (ie no high
> current messages). Is there something about the RF peaks on SSB, do they
> overshoot sometimes or is it something to do with rate of rise of the RF
> voltage?
>
>  

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

[George Winship, NC5G]

Martin.Evans-2 wrote

Hello, I've recently started to use my K2/KPA100 on SSB running 100W
with an MH2 mike mostly on 80m. I use 2:1 compression and mic preamp is
set to 2. The antenna is an 120ft doublet, 30ft of 300ohm ribbon feeder,
remote mounted z match tuner right under the centre of the doublet and
approx 70ft RG58 coax to the rig. I have no RF earth but neither do I
get much RFI in the house. One end of the antenna is about 10m above the
operating position and I'm on the ground floor. I've had varying reports
on the audio quality. Here are a few things I have done/found:
 
Every now and then I would get a high current message after which my RF
peaks (as shown on the K2 bargraph) would drop right down. My remote
mounted z match tuner uses old broadcast receiver variable caps and I
think one of them might have been flashing on speech peaks. I have
backed off the power to 90W and it seems a lot better. The funny thing
is that when I run at 100W on CW I don't have any probs (ie no high
current messages). Is there something about the RF peaks on SSB, do they
overshoot sometimes or is it something to do with rate of rise of the RF
voltage?
 
When I first start an over on SSB the bargraph follows the speech
waveform and is what I could call "lively" but sometimes it goes very
sluggish and doesn't seem to be following the audio, is this normal.
Sometimes the bargraph seems to disappear altogether.
 
The antenna and tuner are balanced and I've added a choke balun and
various ferrites (inc 3 turns on the mic lead and 4 turns on the power
supply lead) to keep any RF off the rig chassis. I hold the mic about 4
inches away since I thought I might be overdriving the audio.
 
 
I don't think the audio is bad but perhaps not the best I could get out
of the K2. Are there any tests/mods/tricks I could try??

Martin,

I run a K2/100 with same mic and settings as you do. I speak right across the mic face holding the mic right next to my mouth. I get many unsolicited remarks about  how good the audio is. I am using  double bazooka's on 80 and 40 and a multiband wire antenna on the others. My power setting is 105 watts.  You state that you have no RF earth. I would suggest that you try grounding the station to get rid of any stray RF that might be coming in especially on voice peaks. Other than that, the suggestions that Don made will hopefully cure the problem

73, George, NC5G