Re: [Elecraft] k2 audio power

2004-06-15 Thread Jim Brown
You are confusing DC resistance with impedance. The impedance of a transducer
(loudspeaker, microphone, headphones) is a combination of the dc resistance
of the voice coil, the motional impedances, and a resistance that corresponds
to the power converted to sound. Thus, those headphones that look like 72
ohms to you DC ohm meter look more like 150-250 ohms to an audio frequency
source.

An antenna acts the same. If you were to measure the DC resistance of the
wire that makes up your antenna, you might see an ohm or two, yet the
impedance of the antenna may be anywhere from 10-20 ohms for a short mobile
antenna to 40 ohms for a quarter wave vertical to 70 ohms for a dipole to
hundreds of ohms for a longer antenna.  Much of the difference is the
radiation resistance, which is a circuit element that accounts for the power
that is radiated. 

And, in both the antenna and the loudspeaker/headphones, there are reactances
(L and C) that account for the resonances.  In the loudspeaker/headphones
they are mechanical resonances, where in the antenna they are electrical
ones. 

Jim  K9YC

On Tue, 15 Jun 2004 21:32:40 -0700, Rick Dettinger wrote:

>My Sony MDR 7506's have a DC resistance of 72 ohms per side.  Since the
>phones are in parallel, the rig will see about 36 ohms. 

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Re: [Elecraft] k2 audio power

2004-06-15 Thread Rick Dettinger
My Sony MDR 7506's have a DC resistance of 72 ohms per side.  Since the
phones are in parallel, the rig will see about 36 ohms.  I am not sure how
that relates to impedance but it seems in the ballpark.  Heating and
reactance would increase it some but I don't know by how much.  They are
comfortable and very sensitive.  I bought them because of good reviews on
eham.  73 - Rick - K7MW
>
> Sony MDR-7506 and MDR-V6 -- these are standard, large, closed headphones
with
> nice soft cushions, work for for long operating sessions.  These sell in
the
> $100 range.  Sony, being Sony, doesn't put impedance and sensitivity specs
on
> the data sheets that I have, but I suspect they are in the same range as
the
> ER4S's.
>


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Re: [Elecraft] k2 audio power

2004-06-15 Thread Jim Brown
On Mon, 14 Jun 2004 9:20:37 -0400, [EMAIL PROTECTED] wrote:

>When we used a second op for logging and "Y'ed" the headphones it was 
>definitely at full throttle. 

The audio system in a K2 is entirely adequate for serious contesting. 

I suspect you have made a poor choice of headphones. I own several good pairs
of headphones, and all produce plenty of level when used with the K2. What
you are looking for is a good combination of relatively high voltage
sensitivity and moderate load impedance (100-250 ohms). It also helps if both
sets of headphones are similar in this regard.  

The K2 headphone output has resistors in series to limit the output level. If
you hang a low impedance load on it, you lose a lot of level. Many cheap
consumer headphones are on the order of 8-20 ohms, and that is most likely
your problem. 

The headphones I own and have used with the K2 are:  

Etymotic Research ER4S and ER4P -- these are tiny in-ear earphones, super for
lightweight portable operation, and have the additional advantage of
excellent isolation from outside noise. The ER4S's are 100 ohms, 108 dBSPL
for 1 volt input; the ER4P's are 27 ohms, 108 dBSPL for 0.25 volts. These are
precision professional units and aren't cheap, but the company makes a lower
cost version (about $100 list) that should be fine for ham radio.  Shure also
makes a product like this for the in-ear monitors that they sell to
musicians. 

Sony MDR-7506 and MDR-V6 -- these are standard, large, closed headphones with
nice soft cushions, work for for long operating sessions.  These sell in the
$100 range.  Sony, being Sony, doesn't put impedance and sensitivity specs on
the data sheets that I have, but I suspect they are in the same range as the
ER4S's. 

Technics RP-HT220 -- similar to the Sony units, not as nice, no longer made.

All combinations of two pairs of these headphones are plenty loud enough when
both are plugged into the K2 at the same time.   

AKG and Sennheiser also make good headphones of this type.  When translating
sensitivity specs, remember that dB is 20 log (V2/V1) and 10 log (P2/P1).  So
the ER4S and ER4P have the same power sensitivity. 

Jim Brown  K9YC
Audio Systems Group, Inc.
Chicago
http://audiosystemsgroup.com


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Re: [Elecraft] k2 audio power

2004-06-15 Thread Ian J Maude
On Mon, 2004-06-14 at 14:20, [EMAIL PROTECTED] wrote:

> The main complaint from all operators was audio power.  There are 2
> stations in the truck, and it is noisy with all of the amplifier fans
> and other local qrm. The volume knob on the k2 was never set below 3/4
> to full for the entire weekend.  When we used a second op for logging
> and "Y'ed" the headphones it was definitely at full throttle. 
I have seen this a few times now and I wonder what serial number your
rig is?  There is a mod to increase the audio power in the archives.
Personally, #4044 has more than enough audio and I have never had it
more than about half way up, even when operating outside!  If it gets
noisy I use a headset (Heil) and I am fine.
Is it just my rig then or does the audio vary so much?

Ian

-- 
Ian Maude G0VGS Morecambe Lancs UK | [EMAIL PROTECTED]
Sysop of GB7MBC, the Morecambe Bay Cluster
Running Linux and DXSpider : K2 #4044
 
Find out about Summits on the Air!  
Visit the SOTA web site at http://www.sota.org.uk

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Re: [Elecraft] k2 audio power

2004-06-14 Thread rwmcgwier
Ed:

I used two K2's at W3CCX over the weekend.  I found one of them to be
usable under the multimulti conditions.  That was not mine, but one built
by John Sortor, KB3XG.  He had mounted an auxiliary audio amplifier
in the lid and it made a world of difference.

We did over a million points for the first time in Packrats history.  I will be
adding external amplifiers to the ones I will be using for FD (2 transmitter,
K2 QRP with AB2KT, W2GD, N2NT, N2NC, W2RQ, and other FRC'ers that
show up) because it is simply a requirement for this kind of noisy environment.

Bob
N4HY


> Ed and all,
> 
> Audio - I do use an external audio amplifier with the K2.
> 
> CW PTT input - I am in the final stages of testing a mod to provide PTT in
> CW mode.  It involves removing RF Board R1 and R2 and inserting a logic AND
> at that point.
> 
> The only inconvience (which is not likely to be resolved soon) is that the
> same PTT input input used for CW will not function on SSB without manually
> changing an added switch.  The normal mic jack PTT still work as it does
> now, and SSB VOX is not changed.
> 
> If you would like to experiment with me, send me a note and I will scan the
> sheet with the schematic and instructions and send it to you.  It will find
> its way to my website in due time.
> 
> 73,
> Don W3FPR
> 
> Life is what happens when you are making other plans
> - Original Message - 
> 
> >
> > I will at least add an external audio amp, but an internal mod would be
> good because I think it would be usefull even at home.
> >
> > There were other complaints too, but minor in nature.  Manual PTT for cw
> being one of the other problems.  With all of the external sequencing
> required for transverters and preamps and power amps, it would really be
> nice if the k2 would switch to tx when I pounce on the footswitch in cw.
> >
> > Other than that we pulled out the weak ones!  Also, the agc off function
> was used well to make a couple of meteor contacts on 222.  Lots of nice
> pings overnight.
> >
> > Ed wa3drc
> >
> 
> 
> 
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Re: [Elecraft] k2 audio power

2004-06-14 Thread Don Wilhelm
Ed and all,

Audio - I do use an external audio amplifier with the K2.

CW PTT input - I am in the final stages of testing a mod to provide PTT in
CW mode.  It involves removing RF Board R1 and R2 and inserting a logic AND
at that point.

The only inconvience (which is not likely to be resolved soon) is that the
same PTT input input used for CW will not function on SSB without manually
changing an added switch.  The normal mic jack PTT still work as it does
now, and SSB VOX is not changed.

If you would like to experiment with me, send me a note and I will scan the
sheet with the schematic and instructions and send it to you.  It will find
its way to my website in due time.

73,
Don W3FPR

Life is what happens when you are making other plans
- Original Message - 

>
> I will at least add an external audio amp, but an internal mod would be
good because I think it would be usefull even at home.
>
> There were other complaints too, but minor in nature.  Manual PTT for cw
being one of the other problems.  With all of the external sequencing
required for transverters and preamps and power amps, it would really be
nice if the k2 would switch to tx when I pounce on the footswitch in cw.
>
> Other than that we pulled out the weak ones!  Also, the agc off function
was used well to make a couple of meteor contacts on 222.  Lots of nice
pings overnight.
>
> Ed wa3drc
>



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[Elecraft] k2 audio power

2004-06-14 Thread edfinn1
All,

I am just returning from a mountaintop weekend running the June QSO party in a 
multi-op environment.  The k2 I supplied for the 222 station worked great, but 
there were several complaints, and I will be attempting to fix these before 
it's next excursion into this environment.

The main complaint from all operators was audio power.  There are 2 stations in 
the truck, and it is noisy with all of the amplifier fans and other local qrm. 
The volume knob on the k2 was never set below 3/4 to full for the entire 
weekend.  When we used a second op for logging and "Y'ed" the headphones it was 
definitely at full throttle. 

I will at least add an external audio amp, but an internal mod would be good 
because I think it would be usefull even at home.

There were other complaints too, but minor in nature.  Manual PTT for cw being 
one of the other problems.  With all of the external sequencing required for 
transverters and preamps and power amps, it would really be nice if the k2 
would switch to tx when I pounce on the footswitch in cw.

Other than that we pulled out the weak ones!  Also, the agc off function was 
used well to make a couple of meteor contacts on 222.  Lots of nice pings 
overnight.

Ed wa3drc 


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