[WriteLog] Audio Situation & RF

K6VVA dx35 at hilding.com
Mon Nov 21 17:15:30 EST 2005


TNX again for the multitude of direct emails and several posts of 
ideas.  I'm posting a more detailed explanation here as I suspect more than 
one person out there may be wrestling with some of this, or will be, but 
perhaps a bit shy about asking for help.

SS is now over.  I finally got on at 0125 Zulu (about 4.5 hours after the 
start)...no DVK /SSB message capabilities this year...only a mic (like the 
"Good Old Days").  Umh, I really never want to have to "manually" call "CQ 
Contest" again in my life !!!

I do believe a minor tweak to future version of WL would give anyone in 
need more "flexibility" for handling audio routing to fit any *specific* 
setup needs.  A simple config option based upon Microsoft's "Where Do You 
Want To Go Today" (or something like that) could eliminate some potential 
headaches...especially in dealing with what I will term FLAKY Stereo 2 Mono 
audio adaptors.

Config Example:

1. ___ Let WL switch audio L-R by default

2. ___ Combine L & R audio into "TRUE" Mono

3. ___ etc., etc.

This would have made life much, much easier.  After 5 trips to Radio Shack 
on Friday, Saturday Morning & Saturday Afternoon (DURING SS), I think I 
have enough stuff cables and adaptors hee to almost open my own 
store.  None of the alleged "Stereo To Mono" cables or adaptors worked. 
IMHO, there should be a law against labeling anything as a Stereo 2 Mono 
adaptor that doesn't do just that...combine the L & R sources into a "Mono" 
output ;-(

Some folks said just tie the L & R wires together, whereas another person 
said that could potentially damage/short out my Notebook audio card.  Talk 
about indecisiveness here for a few hours!!!  I finally bit the bullet 
Saturday Morning & cut a Stereo Cable in two and wrapped the L-R wires 
together and *THAT* part worked.  I tried going directly from the Notebook 
computer audio out into the DXD (that worked...dunno why I never thought of 
it before...TNX!), but unfortunately, plugging the Heil into the soundcard 
"Mic In" doesn't work.  Well, it does, separately, but you have to click 
the "Record" button (I've recorded that way before outside of WL).  I tried 
every setting I could find but simply "No Joy".  My thoughts are that going 
this route, even if it worked, will add more unnecessary noise into the mic 
line.  SignaLink recommends turning off any soundcard options other than 
what's needed to get the .wav file audio out due to the VOX sensitivity 

For portable & Expedition purposes, the SignaLink still remains a good 
choice for use with a Notebook computer because they are extremely small, 
lightweight, and carrying a 2nd unit as a safety backup...I can slip it 
inside a jacket pocket.  So yes, things are a bit more "complicated" here 
due to fixed AND portable operation needs.

The original purpose of the external VOX operated audio card(s) was 
prior-to SO2R plans. I checked into a Rigblaster at HRO on Friday, but they 
didn't have the PRO version and in any event I'm max'd out on IRQ's for 
another USB to Serial interface since I'm already using several for rig 
control from the Notebook (this makes things more challenging vs. 
Standalone computers).

Had the SignaLink folks not been short on parts to modify my 2nd unit, due 
to the way WL handles the audio ("Non-Negotiable"), I would have still had 
the problem.  My bad for not getting at least the one unit back from them 
until two days before SS ;-)

Saturday Morning, I went to my tech-buddy's place with a box full of Radio 
Shack parts, and we built a little "Black Box" with a 12vdc relay to switch 
the audio/mic lines from L-R radios with a Heil Footswich.  The plan was to 
have the mic & .wav file audio switched by the normal Amp-keyline coming 
out of the f/switch, and the DXD PTT activated by the 2nd f/switch line 
which is triggered last.  The box connections are:

* SignaLink audio in (handles the Notebook computer audio out) - Relay 
normal routes to DXD audio In
* Heil HC-4 mike input - Relay engergized routes mic to DXD audio In
* Ouput line to DXD Input
* F/Switch line to activate relay
* 12vdc line input

We finished about 1/2 hour before SS, and I rushed home, hooked everything 
up about 1 minute before the Checkered Flag dropped.  The .wav file audio 
worked AOK switching between L & R in WL via the DXD Auto operation.  Then 
I pushed the footswitch and started to speak.  UGH!!!  Bad News audio from 
the mike...even ramping down to only 5watts output...most likely some kind 
of RF problem in spite of the all metal black box (it is really black :-)

So back into town again where my tech pal put some little capacitors across 
each connector jack on the box, which was *supposed* to fix the RF 
problem.  I rushed back home, only to find *** NOT *** ... there was still 
real bad sounding mic audio.  So it was off to Radio Shack again for 
several handfuls RF chokes, which I stuck on every cable.  Still No Joy.

In all of this, the old adage "Every Problem Is An Opportunity" has proven 
to have some merit.  Using only one SignaLink via the DXD (tnx to many for 
the suggestion) will, in fact, work.  This morning, my tech pal suggested 
unplugging the 12vdc line, and putting the Heil mic line into the normally 
static-position input via the Black Box relay (so the Mic connection would 
be routed to the DXD without needing to activate the relay).  *** BINGO *** 
that works OK...at least at 5w, although IMHO, the rather lengthy wire 
leads *inside* the black box from the connectors to the relay still seem 
like this wouldn't be too RF Friendly.  But then again, I am not a tech person.

The relay is only switching the center lead of the audio lines, as my tech 
pal said the connectors/ground side all share a common ground via the 
connector mountings in the metal box.  So, the monster $64,000 question 
that remains, is how on earth to get rid of what appears to be an RF 
problem gumming up the works?  He suggested I may have to use a shielded 
12vdc line.  Should shielded lines be used *** INSIDE *** the box from the 
connectors to the relay contacts?  I believe the Red RCA tipped line from 
the f/switch is shielded cable.

"Isolation Transformers" have been suggested by several (including the 
NA7XX guys on the 3830 post-Net chatter session last night), but I claim 
cluelessness here.  If, in fact, these are a necessary part of the 
solution, I would appreciate any assistance.

My apologies for the lengthy post, but I sincerely hope there may be others 
who can benefit from the info *** BEFORE *** they travel down the same road 
of headaches.  Especially those with dual fixed & portable/Expedition 
station needs.

Sincere TNX & 73...

Rick, K6VVA

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