XV50 cooling

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XV50 cooling

eric norris
I have a late-model xv144 with holes in both top and bottom panels, connected to k3 with milliwatt drive. It runs excessively hot at 10w out in digital mode EME when used one minute on one minute off,  so i dont think  just getting new panels will help you.  I use a small muffin fan blowing air underneath with the xv-144 up on the optional tilt stand and this simple solution works great.

I also use an xv-432 for eme at 10w but its internal fan keeps it cool.

Perhaps if enough people request a retrofit kit with an internal fan for the xv-50 and xv-144 Elecraft would consider it.  I'd pony up. The fan could attach inside the top panel.

73

Eric WD6DBM

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Re: XV50 cooling

Johnny Siu
Yes, Eric, a retro kit is good idea and all new kits should run with such a modification.

73

Johnny VR2XMC



----- 郵件原件 ----
寄件人﹕ Eric <[hidden email]>
收件人﹕ "[hidden email]" <[hidden email]>
傳送日期﹕ 2010/6/4 (五) 2:18:45 AM
主題: [Elecraft] XV50 cooling

I have a late-model xv144 with holes in both top and bottom panels, connected to k3 with milliwatt drive. It runs excessively hot at 10w out in digital mode EME when used one minute on one minute off,  so i dont think  just getting new panels will help you.  I use a small muffin fan blowing air underneath with the xv-144 up on the optional tilt stand and this simple solution works great.

I also use an xv-432 for eme at 10w but its internal fan keeps it cool.

Perhaps if enough people request a retrofit kit with an internal fan for the xv-50 and xv-144 Elecraft would consider it.  I'd pony up. The fan could attach inside the top panel.

73

Eric WD6DBM

Sent from my ePhone (I wish)
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Re: XV50 cooling

Don Wilhelm-4
In reply to this post by eric norris
Eric,

Have you actually measured the temperature rise?  I am interested in
just how much is "excessively hot".
While it does get warm, I have always found the temperatures to be well
within spec for the output module.

I have an XV50 here for repair right now.  It is next in line for work,
and I intend to get to it this weekend.  After it is repaired, I will
measure the temperature rise on the bottom panel right under the heat
spreader.  I have a Fluke 279 with a temperature probe available.

Report on Monday.

73,
Don W3FPR

Eric wrote:

> I have a late-model xv144 with holes in both top and bottom panels, connected to k3 with milliwatt drive. It runs excessively hot at 10w out in digital mode EME when used one minute on one minute off,  so i dont think  just getting new panels will help you.  I use a small muffin fan blowing air underneath with the xv-144 up on the optional tilt stand and this simple solution works great.
>
> I also use an xv-432 for eme at 10w but its internal fan keeps it cool.
>
> Perhaps if enough people request a retrofit kit with an internal fan for the xv-50 and xv-144 Elecraft would consider it.  I'd pony up. The fan could attach inside the top panel.
>
> 73
>
> Eric WD6DBM
>
>  
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Re: XV50 cooling

Johnny Siu
Hello Don,

The situation is - after I operate either XV144 or XV50 for a 10-15 minutes QSO under 10w FM or 20 w SSB (the advertised rated output from Elecraft, p.3 of the owner's manual), the bottom plate (or even one of side panels) is too hot to be touched. 

I would be very interested in your findings and fully appreciate your knowledge of Elecraft products. After your test, I would be grateful if you could advise, it is all ok to operate the XV50 / XV144 under Elecraft's rated output WITHOUT the need of any modifications to remedy the heat issues.

It would be of great assistance if you could give your advice about the maximum length of any QSO under the rated output.  In other words, say for example, I should not use the XV50 / XV144 for any QSO longer than 15 minutes.  Or, there should be 5 minutes cooling time between each 15 minutes QSO etc.

Thanks a lot in advance and look forward to your results.

73

Johnny VR2XMC



----- 郵件原件 ----
寄件人﹕ Don Wilhelm <[hidden email]>
收件人﹕ Eric <[hidden email]>
副本(CC) "[hidden email]" <[hidden email]>
傳送日期﹕ 2010/6/4 (五) 7:18:59 AM
主題: Re: [Elecraft] XV50 cooling

Eric,

Have you actually measured the temperature rise?  I am interested in
just how much is "excessively hot".
While it does get warm, I have always found the temperatures to be well
within spec for the output module.

I have an XV50 here for repair right now.  It is next in line for work,
and I intend to get to it this weekend.  After it is repaired, I will
measure the temperature rise on the bottom panel right under the heat
spreader.  I have a Fluke 279 with a temperature probe available.

Report on Monday.

73,
Don W3FPR

Eric wrote:

> I have a late-model xv144 with holes in both top and bottom panels, connected to k3 with milliwatt drive. It runs excessively hot at 10w out in digital mode EME when used one minute on one minute off,  so i dont think  just getting new panels will help you.  I use a small muffin fan blowing air underneath with the xv-144 up on the optional tilt stand and this simple solution works great.
>
> I also use an xv-432 for eme at 10w but its internal fan keeps it cool.
>
> Perhaps if enough people request a retrofit kit with an internal fan for the xv-50 and xv-144 Elecraft would consider it.  I'd pony up. The fan could attach inside the top panel.
>
> 73
>
> Eric WD6DBM
>



     

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Re: Re: XV50 cooling

Don Wilhelm-4
Johnny,

Be confident that I will test at the 10 watt level (simulated FM) for a
significant length of time, and also Eric's situation - 10 watts, 1
minute on, 1 minute off.  I did similar stress testing on both large and
small devices for the last 10 years of my professional career - I am
quite familiar with the procedures required to test to specification -
unfortunately, I do not have an environmental chamber available anymore
to conduct the test at the highest ambient temperature allowed for the
assembly, we will have to settle for a temperature rise measurement and
extrapolate from there.

If the temperature goes above the power module's spec, I will terminate
the test early (I don't want to produce a failure in someone else's
transverter), but will attempt to run for your suggested period of time
if the temperature stays within spec.  Elecraft rates the transverters
at 10 watts continuous duty and 20 watts intermittent, the output module
is rated at 30 watts ICAS by the manufacturer, so Elecraft's rating
should be conservative.

This XV50 does have the vent holes on the bottom panel.

While it is nice to keep things cool, sometimes the device manufacturer
expects things to get too hot to touch comfortably.  Despite my thoughts
that it may be hotter than desirable, I have to have faith that the
device manufacturer has done sufficient testing to substantiate his
specifications - users should "hold the manufacturer's feet to the fire"
if that is not true.  We will see.

73,
Don W3FPR

Johnny Siu wrote:

> Hello Don,
>
> The situation is - after I operate either XV144 or XV50 for a 10-15 minutes QSO under 10w FM or 20 w SSB (the advertised rated output from Elecraft, p.3 of the owner's manual), the bottom plate (or even one of side panels) is too hot to be touched.  
>
> I would be very interested in your findings and fully appreciate your knowledge of Elecraft products. After your test, I would be grateful if you could advise, it is all ok to operate the XV50 / XV144 under Elecraft's rated output WITHOUT the need of any modifications to remedy the heat issues.
>
> It would be of great assistance if you could give your advice about the maximum length of any QSO under the rated output.  In other words, say for example, I should not use the XV50 / XV144 for any QSO longer than 15 minutes.  Or, there should be 5 minutes cooling time between each 15 minutes QSO etc.
>
> Thanks a lot in advance and look forward to your results.
>
> 73
>
> Johnny VR2XMC
>
>
>
> ----- 郵件原件 ----
> 寄件人﹕ Don Wilhelm <[hidden email]>
> 收件人﹕ Eric <[hidden email]>
> 副本(CC) "[hidden email]" <[hidden email]>
> 傳送日期﹕ 2010/6/4 (五) 7:18:59 AM
> 主題: Re: [Elecraft] XV50 cooling
>
> Eric,
>
> Have you actually measured the temperature rise?  I am interested in
> just how much is "excessively hot".
> While it does get warm, I have always found the temperatures to be well
> within spec for the output module.
>
> I have an XV50 here for repair right now.  It is next in line for work,
> and I intend to get to it this weekend.  After it is repaired, I will
> measure the temperature rise on the bottom panel right under the heat
> spreader.  I have a Fluke 279 with a temperature probe available.
>
> Report on Monday.
>
> 73,
> Don W3FPR
>
> Eric wrote:
>  
>> I have a late-model xv144 with holes in both top and bottom panels, connected to k3 with milliwatt drive. It runs excessively hot at 10w out in digital mode EME when used one minute on one minute off,  so i dont think  just getting new panels will help you.  I use a small muffin fan blowing air underneath with the xv-144 up on the optional tilt stand and this simple solution works great.
>>
>> I also use an xv-432 for eme at 10w but its internal fan keeps it cool.
>>
>> Perhaps if enough people request a retrofit kit with an internal fan for the xv-50 and xv-144 Elecraft would consider it.  I'd pony up. The fan could attach inside the top panel.
>>
>> 73
>>
>> Eric WD6DBM
>>
>>  
>>    
>
>
>
>      
>
> ______________________________________________________________
> Elecraft mailing list
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> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
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> Please help support this email list: http://www.qsl.net/donate.html
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Re: XV50 cooling

n0jrn
In reply to this post by eric norris
Evening gang:

Just got home from work and reading my male.    I looked at the manual for
the XV432 to see how the internal fan is mounted and how it was hooked up.
It really doesn't look like much of a task to modify my XV50 and install
such a fan.

I contacted sales and was told the vented panels are not available.  As much
as I hate drilling my own panels  ( don't like messing up the paint )   I
see very little challenge in copying what Elecraft did with the 432 version.

I will wait Don, to hear the results of your tests before doing anything.

73 to all;             Jerry         N0JRN

On 6/3/2010 1:18:45 PM, Eric ([hidden email]) wrote:
> I have a late-model xv144 with holes in both top and bottom panels,
> connected to k3 with milliwatt drive. It runs excessively hot at 10w out

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Re: Re: XV50 cooling

Don Wilhelm-5
In reply to this post by Johnny Siu
Johnny,

Prior to testing, I have reviewed the datasheet for the RA30H0608M
module that is used in the XV50.  The power module is specified to
operate within spec at 110 degrees C ( 230 deg F).  While that is too
hot to touch (in excess of boiling water temperatures), it is well
within the device specifications.
I am looking at the Mitsubishi data sheet for the RA30H0608M device.

I will see what my tests reveal, but I believe the answer will be that
the temperature is well within the device specifications.

The MTBF for the device is not specified in the datasheet, but it ia a
well known fact that the MTBF for any device decreases with the
operating temperature.  So the early answer is that the output module
will likely operate within its specified temperature range, its
longevity might be extended by providing extra cooling to reduce its
operating temperature.

Testing will reveal the actual temperature rise - details later.

73,
Don W3FPR

Johnny Siu wrote:

> Hello Don,
>
> The situation is - after I operate either XV144 or XV50 for a 10-15 minutes QSO under 10w FM or 20 w SSB (the advertised rated output from Elecraft, p.3 of the owner's manual), the bottom plate (or even one of side panels) is too hot to be touched.  
>
> I would be very interested in your findings and fully appreciate your knowledge of Elecraft products. After your test, I would be grateful if you could advise, it is all ok to operate the XV50 / XV144 under Elecraft's rated output WITHOUT the need of any modifications to remedy the heat issues.
>
> It would be of great assistance if you could give your advice about the maximum length of any QSO under the rated output.  In other words, say for example, I should not use the XV50 / XV144 for any QSO longer than 15 minutes.  Or, there should be 5 minutes cooling time between each 15 minutes QSO etc.
>
> Thanks a lot in advance and look forward to your results.
>
> 73
>
> Johnny VR2XMC
>
>
>
> ----- 郵件原件 ----
> 寄件人﹕ Don Wilhelm <[hidden email]>
> 收件人﹕ Eric <[hidden email]>
> 副本(CC) "[hidden email]" <[hidden email]>
> 傳送日期﹕ 2010/6/4 (五) 7:18:59 AM
> 主題: Re: [Elecraft] XV50 cooling
>
> Eric,
>
> Have you actually measured the temperature rise?  I am interested in
> just how much is "excessively hot".
> While it does get warm, I have always found the temperatures to be well
> within spec for the output module.
>
> I have an XV50 here for repair right now.  It is next in line for work,
> and I intend to get to it this weekend.  After it is repaired, I will
> measure the temperature rise on the bottom panel right under the heat
> spreader.  I have a Fluke 279 with a temperature probe available.
>
> Report on Monday.
>
> 73,
> Don W3FPR
>
> Eric wrote:
>  
>> I have a late-model xv144 with holes in both top and bottom panels, connected to k3 with milliwatt drive. It runs excessively hot at 10w out in digital mode EME when used one minute on one minute off,  so i dont think  just getting new panels will help you.  I use a small muffin fan blowing air underneath with the xv-144 up on the optional tilt stand and this simple solution works great.
>>
>> I also use an xv-432 for eme at 10w but its internal fan keeps it cool.
>>
>> Perhaps if enough people request a retrofit kit with an internal fan for the xv-50 and xv-144 Elecraft would consider it.  I'd pony up. The fan could attach inside the top panel.
>>
>> 73
>>
>> Eric WD6DBM
>>
>>  
>>    
>
>
>
>      
>
>
>  
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Re: XV50 cooling

eric norris
In reply to this post by eric norris
Well, as I recall I could not hold my hand on it, but i only ran it without a fan once when I first built it and my memory is hazy.  

 Remember digital EME is one minute on, one minute off for hours. I have run four hours at a time that way without a break, and I'm sure others run longer.

Maybe it was still in spec, but why push it?  All that extra heat can't possibly make the XV more stable or less prone to failure than if it were running at room temp. Mine does have the xtal oven if that makes a difference.  I don't know how much heat that adds to the system.

73,

Eric WD6DBM

Sent from my iPhone

On Jun 3, 2010, at 4:18 PM, Don Wilhelm <[hidden email]> wrote:

Eric,

Have you actually measured the temperature rise?  I am interested in just how much is "excessively hot".
While it does get warm, I have always found the temperatures to be well within spec for the output module.

I have an XV50 here for repair right now.  It is next in line for work, and I intend to get to it this weekend.  After it is repaired, I will measure the temperature rise on the bottom panel right under the heat spreader.  I have a Fluke 279 with a temperature probe available.

Report on Monday.

73,
Don W3FPR

Eric wrote:
I have a late-model xv144 with holes in both top and bottom panels, connected to k3 with milliwatt drive. It runs excessively hot at 10w out in digital mode EME when used one minute on one minute off,  so i dont think  just getting new panels will help you.  I use a small muffin fan blowing air underneath with the xv-144 up on the optional tilt stand and this simple solution works great.
I also use an xv-432 for eme at 10w but its internal fan keeps it cool.
Perhaps if enough people request a retrofit kit with an internal fan for the xv-50 and xv-144 Elecraft would consider it.  I'd pony up. The fan could attach inside the top panel.
73

Eric WD6DBM
 

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Re: Re: XV50 cooling

eric norris
In reply to this post by Johnny Siu
Don, some other considerations:

1). What about the other components inside the XV?  If the power module is happy running at 100C what does that do for everything else in the XV running at 60-70C with no airflow?

2). My ambient temp in the shack during EME is 80F even with the house A/C running due to the tube PA.

3). Does the XV144 run at the same efficiency (waste heat output) as the XV50?

Thanks for your assistance. I look forward to your measurements.

73

Eric WD6DBM

Sent from my iPhone

On Jun 3, 2010, at 9:02 PM, Don Wilhelm <[hidden email]> wrote:

Johnny,

Prior to testing, I have reviewed the datasheet for the RA30H0608M module that is used in the XV50.  The power module is specified to operate within spec at 110 degrees C ( 230 deg F).  While that is too hot to touch (in excess of boiling water temperatures), it is well within the device specifications.  SNIP




















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Re: Re: XV50 cooling

Johnny Siu
Hello Eric,

XV144 is basically the same structure as XV50.  I have both XV50 and Xv144.

cheers,

Johnny VR2XMC



----- 郵件原件 ----
寄件人﹕ Eric <[hidden email]>
收件人﹕ "[hidden email]" <[hidden email]>
副本(CC) Johnny Siu <[hidden email]>; "[hidden email]" <[hidden email]>
傳送日期﹕ 2010/6/4 (五) 1:46:42 PM
主題: Re: Re: [Elecraft] XV50 cooling

Don, some other considerations:

1). What about the other components inside the XV?  If the power module is happy running at 100C what does that do for everything else in the XV running at 60-70C with no airflow?

2). My ambient temp in the shack during EME is 80F even with the house A/C running due to the tube PA.

3). Does the XV144 run at the same efficiency (waste heat output) as the XV50?

Thanks for your assistance. I look forward to your measurements.

73

Eric WD6DBM

Sent from my iPhone

On Jun 3, 2010, at 9:02 PM, Don Wilhelm <[hidden email]> wrote:

Johnny,

Prior to testing, I have reviewed the datasheet for the RA30H0608M module that is used in the XV50.  The power module is specified to operate within spec at 110 degrees C ( 230 deg F).  While that is too hot to touch (in excess of boiling water temperatures), it is well within the device specifications.  SNIP


     

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Re: XV50 cooling

Don Wilhelm-4
In reply to this post by Don Wilhelm-4
Gentleman,

My promised temperature rise measurements will have to be delayed a
bit.  This XV50 has a bad power output module and I will have to wait
for one to be sent from Watsonville.  Later next week, I will have the data.

BTW - Mitsubishi in their notes at the end of the data sheet suggest
that the module case temperature should be limited to 60 deg/C - but
that is "too hot to touch" (140 deg/F), so the "excessively hot"
criteria may actually be well within the limits of tolerance - I would
not want to hold my hand very long on a surface that is at 60 deg/C.  
Also, I do agree that other components can be affected by the
temperature rise, but most are spec-ed at 60 deg/C, so in reality, there
may be no problem, just a "discomfort zone" - details after the new
module arrives.

73,
Don W3FPR

Don Wilhelm wrote:

> Eric,
>
> Have you actually measured the temperature rise?  I am interested in
> just how much is "excessively hot".
> While it does get warm, I have always found the temperatures to be well
> within spec for the output module.
>
> I have an XV50 here for repair right now.  It is next in line for work,
> and I intend to get to it this weekend.  After it is repaired, I will
> measure the temperature rise on the bottom panel right under the heat
> spreader.  I have a Fluke 279 with a temperature probe available.
>
> Report on Monday.
>
> 73,
> Don W3FPR
>
> Eric wrote:
>  
>> I have a late-model xv144 with holes in both top and bottom panels, connected to k3 with milliwatt drive. It runs excessively hot at 10w out in digital mode EME when used one minute on one minute off,  so i dont think  just getting new panels will help you.  I use a small muffin fan blowing air underneath with the xv-144 up on the optional tilt stand and this simple solution works great.
>>
>> I also use an xv-432 for eme at 10w but its internal fan keeps it cool.
>>
>> Perhaps if enough people request a retrofit kit with an internal fan for the xv-50 and xv-144 Elecraft would consider it.  I'd pony up. The fan could attach inside the top panel.
>>
>> 73
>>
>> Eric WD6DBM
>>
>>  
>>    
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html
>
>  
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Re: XV50 cooling

Geoffrey Mackenzie-Kennedy
Don,

I do not like to add to your workload, but I would be interested to know if
the heat generated by the Mitsubishi power module has any negative effect on
the transverter's noise figure (receive mode) if you have the time to
measure it. If I understand the layout of the XV50 correctly, the input
circuitry of its receive path is placed quite close to the power module.

My reason for asking is that I have been considering the option of buying a
XV50 for use in a set up dedicated only to 6m EME, rather than building a
transverter from scratch

73,
Geoff
GM4ESD


Don Wilhelm wrote on Sunday, June 06, 2010 at 3:59 AM:



> Gentleman,
>
> My promised temperature rise measurements will have to be delayed a
> bit.  This XV50 has a bad power output module and I will have to wait
> for one to be sent from Watsonville.  Later next week, I will have the
> data.
>
> BTW - Mitsubishi in their notes at the end of the data sheet suggest
> that the module case temperature should be limited to 60 deg/C - but
> that is "too hot to touch" (140 deg/F), so the "excessively hot"
> criteria may actually be well within the limits of tolerance - I would
> not want to hold my hand very long on a surface that is at 60 deg/C.
> Also, I do agree that other components can be affected by the
> temperature rise, but most are spec-ed at 60 deg/C, so in reality, there
> may be no problem, just a "discomfort zone" - details after the new
> module arrives.
>
> 73,
> Don W3FPR




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Re: XV50 cooling

Don Wilhelm-4
Geoff,

I do not have proper equipment to do a true noise figure measurement,
but my signal generator will go down to -140 dBm, and I can give the
number of dB above the receive noise floor for that signal strength - I
can do that at various temperatures during the other tests.

I doubt the temperature rise will affect the active devices, but a
change in temperature *could* alter the inductors a bit which could
detune the input circuits slightly.  At this point, that is all speculation.

73,
Don W3FPR

Geoffrey Mackenzie-Kennedy wrote:

> Don,
>
> I do not like to add to your workload, but I would be interested to know if
> the heat generated by the Mitsubishi power module has any negative effect on
> the transverter's noise figure (receive mode) if you have the time to
> measure it. If I understand the layout of the XV50 correctly, the input
> circuitry of its receive path is placed quite close to the power module.
>
> My reason for asking is that I have been considering the option of buying a
> XV50 for use in a set up dedicated only to 6m EME, rather than building a
> transverter from scratch
>
> 73,
> Geoff
> GM4ESD
>
>
> Don Wilhelm wrote on Sunday, June 06, 2010 at 3:59 AM:
>
>
>
>  
>> Gentleman,
>>
>> My promised temperature rise measurements will have to be delayed a
>> bit.  This XV50 has a bad power output module and I will have to wait
>> for one to be sent from Watsonville.  Later next week, I will have the
>> data.
>>
>> BTW - Mitsubishi in their notes at the end of the data sheet suggest
>> that the module case temperature should be limited to 60 deg/C - but
>> that is "too hot to touch" (140 deg/F), so the "excessively hot"
>> criteria may actually be well within the limits of tolerance - I would
>> not want to hold my hand very long on a surface that is at 60 deg/C.
>> Also, I do agree that other components can be affected by the
>> temperature rise, but most are spec-ed at 60 deg/C, so in reality, there
>> may be no problem, just a "discomfort zone" - details after the new
>> module arrives.
>>
>> 73,
>> Don W3FPR
>>    
>
>
>
>
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Re: XV50 cooling

Geoffrey Mackenzie-Kennedy
Don,

Thank you.

Yes it is the possible effect on the input L-C circuit that is my main
concern.

73,

Geoff
GM4ESD


Don Wilhelm wrote:

> Geoff,
>
> I do not have proper equipment to do a true noise figure measurement,
> but my signal generator will go down to -140 dBm, and I can give the
> number of dB above the receive noise floor for that signal strength - I
> can do that at various temperatures during the other tests.
>
> I doubt the temperature rise will affect the active devices, but a
> change in temperature *could* alter the inductors a bit which could
> detune the input circuits slightly.  At this point, that is all
> speculation.
>
> 73,
> Don W3FPR




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Re: XV50 cooling

W8JI
> Yes it is the possible effect on the input L-C circuit
> that is my main
> concern.
>
> 73,
>
> Geoff
> GM4ESD

I would think the major concern would be elevated noise or
change in the first stage's semiconductor device parameters
from the receiver's input device temperature increase, not
from tuned circuit drift or PA noise.

I can't imagine a tuned circuit wide enough to pass six
meters drifting so far as to change sensitivity, or really
any meaningful change on a band like six meters.

73 Tom

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Re: XV50 cooling

Johnny Siu
Hello Gentleman,

The structure and architectural of XV50 and XV144 are the same.  The proposed test from Don would be useful.  Eventually, we do need an official confirmation from Elecraft some time in due course.  Let us stay tune and wait for Don's test.

cheers,

Johnny VR2XMC



----- 郵件原件 ----
寄件人﹕ Tom W8JI <[hidden email]>
收件人﹕ Geoffrey Mackenzie-Kennedy <[hidden email]>; [hidden email]
副本(CC) Elecraft Discussion List <[hidden email]>
傳送日期﹕ 2010/6/6 (日) 9:43:59 PM
主題: Re: [Elecraft] XV50 cooling

> Yes it is the possible effect on the input L-C circuit
> that is my main
> concern.
>
> 73,
>
> Geoff
> GM4ESD

I would think the major concern would be elevated noise or
change in the first stage's semiconductor device parameters
from the receiver's input device temperature increase, not
from tuned circuit drift or PA noise.

I can't imagine a tuned circuit wide enough to pass six
meters drifting so far as to change sensitivity, or really
any meaningful change on a band like six meters.

73 Tom

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Re: XV50 cooling

Geoffrey Mackenzie-Kennedy
In reply to this post by W8JI
Would that not depend on whether or not the source impedance presented to
the input device has been optimised for lowest noise figure or for optimum
power transfer? If the former then the question arises how rapidly does the
noise figure change with small deviations from an optimum noise "match",
even if the effective loaded Q of the input circuitry is suitable to pass
the six metre band.

I agree that the noise figure need not be very low for terrestrial 6m, but
6m EME requires much lower noise figures when looking away from manmade
noise sources.

73,
Geoff.


Tom W8JI wrote:

> I would think the major concern would be elevated noise or
> change in the first stage's semiconductor device parameters
> from the receiver's input device temperature increase, not
> from tuned circuit drift or PA noise.
>
> I can't imagine a tuned circuit wide enough to pass six
> meters drifting so far as to change sensitivity, or really
> any meaningful change on a band like six meters.
>
> 73 Tom



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Re: XV50 cooling

W8JI
> Would that not depend on whether or not the source
> impedance presented to the input device has been optimised
> for lowest noise figure or for optimum power transfer? If
> the former then the question arises how rapidly does the
> noise figure change with small deviations from an optimum
> noise "match", even if the effective loaded Q of the input
> circuitry is suitable to pass the six metre band.

The two primary sources of noise are from current flow in
the input device and thermal noise. I'm not sure what
portion of the two exist in the XV50, but almost certainly
the semiconductor characteristics would change far more
rapidly than the impedance of relatively broadly tuned
matching circuits.
 

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