#18

Good Morning,

I just received/built a "Run 4" box. It seems to work fine until I transmit local SSB audio at any power level over 2W. From 2W up, what appears to be RF feedback into the mic line causes the transmitter to generate ugly noise at full amplitude. Classic RFI into the mic line, which I've struggled with in decades past. 

Is there an easy cure? I'm thinking of adding several pF on both ends of the mic audio line on the PC board (each DIN as well as the 3.5mm mic input). I'd appreciate anyone providing a startinig point.

Notes:
1. Ferrites (lots of 'em) on the DIN cable have little or no effect. Maybe lets out another half watt.
2. The RX audio was oscillating upon first power up due to the floating ground on this Run 4 board. The ND2T jumper was added; problem sollved. (TU Tom).  I don't think this has any influence on the mic line.
3. Mic is a Heil HC4. Rig is a K4. The 14 dB mic preamp is required for full output. RFI occurs without the preamp, but at a much higher power level, as you would expect. DIN cable to rig is CAT5, using a twisted pair for mic and mic ground.
4. I scraped the paint from the chassis inside at the ground lug mounting screw position.
5. In TX TEST mode (zero RF out), the mic line works fine. Mic directly into the K4 works fine at 1500W.

Thanks for any assistance. CU on the air (?)!

-- 
73 de Bob, K6XX

#19

Hi Bob,

What do you mean by a "Run 4 box"?? I have a K4 but I haven't done any SO2R phone operating with it.

The SO2R Box microphone switching is very simple - there is a relay which connects both the mic hot and ground to the appropriate radio.? The mic ground is not grounded to the box or to the power supply minus.? There isn't a jumper but it would be pretty easy to add a wire which grounds it.

I would try a wire or maybe a capacitor between the mic ground lead and the box ground.? If you do this you'll have to open the box - remember to remove the nut on the speed pot before you open it, otherwise you will break the pot.

??? Paul

Show quoted text

On Sat, Jul 16, 2022 at 2:22 PM Bob Wolbert, K6XX <k6xx@...> wrote:

Good Morning,

I just received/built a "Run 4" box. It seems to work fine until I transmit local SSB audio at any power level over 2W. From 2W up, what appears to be RF feedback into the mic line causes the transmitter to generate ugly noise at full amplitude. Classic RFI into the mic line, which I've struggled with in decades past.

Is there an easy cure? I'm thinking of adding several pF on both ends of the mic audio line on the PC board (each DIN as well as the 3.5mm mic input). I'd appreciate anyone providing a startinig point.

Notes:
1. Ferrites (lots of 'em) on the DIN cable have little or no effect. Maybe lets out another half watt.
2. The RX audio was oscillating upon first power up due to the floating ground on this Run 4 board. The ND2T jumper was added; problem sollved. (TU Tom).? I don't think this has any influence on the mic line.
3. Mic is a Heil HC4. Rig is a K4. The 14 dB mic preamp is required for full output. RFI occurs without the preamp, but at a much higher power level, as you would expect. DIN cable to rig is CAT5, using a twisted pair for mic and mic ground.
4. I scraped the paint from the chassis inside at the ground lug mounting screw position.
5. In TX TEST mode (zero RF out), the mic line works fine. Mic directly into the K4 works fine at 1500W.

Thanks for any assistance. CU on the air (?)!

--
73 de Bob, K6XX

#20

Bob

I think by "Run 4", you mean a YCCC box from the fourth run.

The only thing I see that you didn't comment on was that paint needs to be scraped at two spots- one is the

where the ground lug is, and the other is to make sure the board is grounded.? If? you look at the pc board, you

will see that one of the mounting screw holes is connected to the board ground.? Where that screw and?

spreader meet the chassis also needs the paint scraped.? I don't know that that would solve your problem,

but it was in the construction documents.

Dennis W1UE

Show quoted text

On Sun, Jul 17, 2022 at 8:48 PM Paul Young <k1xm@...> wrote:

Hi Bob,

What do you mean by a "Run 4 box"?? I have a K4 but I haven't done any SO2R phone operating with it.

The SO2R Box microphone switching is very simple - there is a relay which connects both the mic hot and ground to the appropriate radio.? The mic ground is not grounded to the box or to the power supply minus.? There isn't a jumper but it would be pretty easy to add a wire which grounds it.

I would try a wire or maybe a capacitor between the mic ground lead and the box ground.? If you do this you'll have to open the box - remember to remove the nut on the speed pot before you open it, otherwise you will break the pot.

??? Paul

On Sat, Jul 16, 2022 at 2:22 PM Bob Wolbert, K6XX <k6xx@...> wrote:
Good Morning,

I just received/built a "Run 4" box. It seems to work fine until I transmit local SSB audio at any power level over 2W. From 2W up, what appears to be RF feedback into the mic line causes the transmitter to generate ugly noise at full amplitude. Classic RFI into the mic line, which I've struggled with in decades past.

Is there an easy cure? I'm thinking of adding several pF on both ends of the mic audio line on the PC board (each DIN as well as the 3.5mm mic input). I'd appreciate anyone providing a startinig point.

Notes:
1. Ferrites (lots of 'em) on the DIN cable have little or no effect. Maybe lets out another half watt.
2. The RX audio was oscillating upon first power up due to the floating ground on this Run 4 board. The ND2T jumper was added; problem sollved. (TU Tom).? I don't think this has any influence on the mic line.
3. Mic is a Heil HC4. Rig is a K4. The 14 dB mic preamp is required for full output. RFI occurs without the preamp, but at a much higher power level, as you would expect. DIN cable to rig is CAT5, using a twisted pair for mic and mic ground.
4. I scraped the paint from the chassis inside at the ground lug mounting screw position.
5. In TX TEST mode (zero RF out), the mic line works fine. Mic directly into the K4 works fine at 1500W.

Thanks for any assistance. CU on the air (?)!

--
73 de Bob, K6XX

#21

Paul, Dennis,

Thank you for replying.

For background, I just received and built this (old stock) kit. "Run 4" is a quote from Dennis's email of 24 Oct 2011 warning about a floating ground on the audio amp that required a shorting jumper to connect them that affects the fourth run of PC boards. A printout of this message was included with the kit. Nothing to do with a K4... radio was mentioned to explain why multiple mic preamps were available.

While I scraped the tenacious powder coat off the ground stud, I missed the part about scraping paint where the board mounts. My mistake!

An ohmmeter shows no continuity between the various connector shields themselves, or between them and chassis. I will run a shorting wire to all of these as well as scrape away more paint. I calculate that about 0.01uF is a good starting point for a bypass capacitor across MIC and MIC GND.

I appreciate your assistance!

In the "No Good Deed Goes Unpunished" department: a comment to any of you crazy enough to consider a similar future product. From direct personal experience, it is unwise to pay chassis fabricators to powder coat the interior of RF-system boxes. While much more attractive and 'professional looking', the paint really gets in the way, even as overspray. In fact, it _is_ wise to pay them to mask the interior of the box where grounded connectors mount, even when the insides are not painted. Now, off my soapbox and on to cleaning up my new SO2R box!

73 de Bob, K6XX
-- 
73 de Bob, K6XX

-- 
73 de Bob, K6XX

#22

... from a person with quarter century In QC department - there's special kind of "aggressive" washes specifically designed to penetrate coating and provide acceptable electrically ground connection.

Show quoted text

-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Bob Wolbert, K6XX
Sent: Monday, July 18, 2022 13:46
To: [email protected]
Subject: Re: [yccc-so2r] RFI Into Mic Line

Paul, Dennis,

Thank you for replying.

For background, I just received and built this (old stock) kit. "Run 4" 
is a quote from Dennis's email of 24 Oct 2011 warning about a floating ground on the audio amp that required a shorting jumper to connect them that affects the fourth run of PC boards. A printout of this message was included with the kit. Nothing to do with a K4... radio was mentioned to explain why multiple mic preamps were available.

While I scraped the tenacious powder coat off the ground stud, I missed the part about scraping paint where the board mounts. My mistake!

An ohmmeter shows no continuity between the various connector shields themselves, or between them and chassis. I will run a shorting wire to all of these as well as scrape away more paint. I calculate that about 0.01uF is a good starting point for a bypass capacitor across MIC and MIC GND.

I appreciate your assistance!

In the "No Good Deed Goes Unpunished" department: a comment to any of you crazy enough to consider a similar future product. From direct personal experience, it is unwise to pay chassis fabricators to powder coat the interior of RF-system boxes. While much more attractive and 'professional looking', the paint really gets in the way, even as overspray. In fact, it _is_ wise to pay them to mask the interior of the box where grounded connectors mount, even when the insides are not painted. Now, off my soapbox and on to cleaning up my new SO2R box!

73 de Bob, K6XX
--
73 de Bob, K6XX

-- 
73 de Bob, K6XX

#23

Some of this is the difference between a ham radio club project and a commercial product.? Originally I built an SO2R Box and brought it to a YCCC meeting.? WW1M saw it and said he could lay out a PC board.? N4BAA said he could design a box.? We expected to build fifteen of them.

??? Paul, K1XM

Show quoted text

On Mon, Jul 18, 2022 at 7:48 PM Bugs Bunny <olegtf@...> wrote:

... from a person with quarter century In QC department - there's special kind of "aggressive" washes specifically designed to penetrate coating and provide acceptable electrically ground connection.

#24

And 750 So2R Boxes later, we had to retire the design because?parts were getting hard to find.

Dennis W1UE

Show quoted text

On Tue, Jul 19, 2022 at 7:48 AM Paul Young <k1xm@...> wrote:

Some of this is the difference between a ham radio club project and a commercial product.? Originally I built an SO2R Box and brought it to a YCCC meeting.? WW1M saw it and said he could lay out a PC board.? N4BAA said he could design a box.? We expected to build fifteen of them.

??? Paul, K1XM

On Mon, Jul 18, 2022 at 7:48 PM Bugs Bunny <olegtf@...> wrote:
... from a person with quarter century In QC department - there's special kind of "aggressive" washes specifically designed to penetrate coating and provide acceptable electrically ground connection.

#25

FWIW, I *LOVE* my YCCC SO2R+ box.? I even got another kit (and built it) somewhere along the way as a backup, just in case !? I am going to build a 3rd to have as a travel-kit, assuming we ever travel again ;-)

The functionality and support from Dennis and others has been A1 ! !

Thanks for all that you do to support this.

73 Mike VE9AA

#26

开云体育

…take apart any old AT or ATX power supply, find ground wire from 110/220V power connector, Ground wire has yellow/green stripes. Remove nut, flat washer and “bity” washer you looking for. Its it folks ?

?

Show quoted text

From: [email protected] <[email protected]> On Behalf Of Paul Young
Sent: Tuesday, July 19, 2022 07:47
To: [email protected]
Subject: Re: [yccc-so2r] RFI Into Mic Line

?

Some of this is the difference between a ham radio club project and a commercial product.? Originally I built an SO2R Box and brought it to a YCCC meeting.? WW1M saw it and said he could lay out a PC board.? N4BAA said he could design a box.? We expected to build fifteen of them.

?

??? Paul, K1XM

?

On Mon, Jul 18, 2022 at 7:48 PM Bugs Bunny <olegtf@...> wrote:

... from a person with quarter century In QC department - there's special kind of "aggressive" washes specifically designed to penetrate coating and provide acceptable electrically ground connection.