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Ameco PT-3

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TR K2 #838

Ameco PT-3

Dear fellow Elecrafters,

I want to report the stunning success the PT-3 has had on the upper
bands. Especially 15 and 10 meters. I have long held the suspicion
that the K2 is deficient in sensitivity on these bands and the PT-3
confirms it in spades. Stations that are indecipherable now stand
out clearly in arm chair copy.

Let me recommend to others to try the PT-3 !

BTW, my K2 has been back to both Gary and Don and has been checked on
the higher bands for sensitivity. It has returned both times with a
testimonial as to it's being OK.

TR, K6GC, the Great Circle Station
in the State of Jefferson.
http://www.ijpr.org/Page.asp?NavID=1033

K2/100/KAT S/N 838, Updated with all the new mods.

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Don Wilhelm-4

Re: Ameco PT-3

Warren,

Great to hear that you have had success with the preamp.

However, the sensitivity of a properly working K2 on 15, 12 and 10
meters is sufficient to make a -136 dBm or lower level signal stand out
well above (greater than 3 dB) the internal noise of the K2. I have
measured many, including yours.

Normally the atmospheric noise on those bands is low, especially during
the current (and extended) sunspot low period, and that allows a
preamplifier to be of value.

The other thing to consider is the antenna (and feedline loss). If
there is not an increase in noise (due to the presence of atmospheric
noise) when you connect the antenna to the K2 (or any other radio), then
a preamp will help.
If there *is* a noise increase when the antenna is connected, then
*usually* a preamp will not help - it will make the atmospheric noise
heard in the audio output greater, but that is not a signal - we
normally do not copy signals buried in the atmospheric noise - although
a few ops have excellent ears for doing just that.

73,
Don W3FPR

Warren & Barbara Reese wrote:

> Dear fellow Elecrafters,
>
> I want to report the stunning success the PT-3 has had on the upper
> bands. Especially 15 and 10 meters. I have long held the suspicion
> that the K2 is deficient in sensitivity on these bands and the PT-3
> confirms it in spades. Stations that are indecipherable now stand
> out clearly in arm chair copy.
>
> Let me recommend to others to try the PT-3 !
>
> BTW, my K2 has been back to both Gary and Don and has been checked on
> the higher bands for sensitivity. It has returned both times with a
> testimonial as to it's being OK.
>
> TR, K6GC, the Great Circle Station
> in the State of Jefferson.
> http://www.ijpr.org/Page.asp?NavID=1033
>
> K2/100/KAT S/N 838, Updated with all the new mods.
>
>

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W8JI

Re: Ameco PT-3

In reply to this post by TR K2 #838

> I want to report the stunning success the PT-3 has had on the upper
> bands. Especially 15 and 10 meters. I have long held the suspicion
> that the K2 is deficient in sensitivity on these bands and the PT-3
> confirms it in spades. Stations that are indecipherable now stand
> out clearly in arm chair copy.

What antenna and antenna system (including feed system) do you have? The
entire antenna system, along with bandwidth and local noise floor, has a
huge effect on things.

As Don pointed out, if we hear a reasonable drop in noise when the antenna
is disconnected (using the narrowest bandwidth in the least noisy direction)
the rig is sensitive enough.

73 Tom

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TR K2 #838

Re: Ameco PT-3

In reply to this post by TR K2 #838

Tom & Don,

Tom,

When the antenna is connected and disconnected the noise floor moves
just barely. You can tell, but it requires a critical ear.

>No, I'm not talking about "antenna noise." I'm talking about
>signals, in particular at 21.150. Using the pre-amp makes signals
>that are unreadable jump out clearly above the K2's noise floor and
>turns them into arm chair copy.

>A note about my antenna. It is a HyGain 5BDQ trap dipole and the
>SWR on it is 1.2:1 into about 200' of LMR240.
_____________________________
Don,

3dB does NOT explain the improvement in the copy of signals received,
it is more like 7 or 8 S units, signal to noise. A quantum improvement !

Warren
________
OK, that helps explain a bit - 200 feet of LMR240 has more loss at 15
meters and above than what I find is acceptable for me. At the shack
end, on 10 meters, the RF voltage is only about half that which is at
the antenna base - approximately 3 dB loss. Your preamp is making up
for that feedline loss.

LMR240 is good feedline, but at higher frequencies and long lengths,
I prefer to use something with less loss - I usually use LMR400.

>>However, the sensitivity of a properly working K2 on 15, 12 and 10
>>meters is sufficient to make a -136 dBm or lower level signal stand
>>out well above (greater than 3 dB) the internal noise of the K2. I
>>have measured many, including yours.
>>
>>Normally the atmospheric noise on those bands is low, especially
>>during the current (and extended) sunspot low period, and that
>>allows a preamplifier to be of value.
>>
>>The other thing to consider is the antenna (and feedline loss). If
>>there is not an increase in noise (due to the presence of
>>atmospheric noise) when you connect the antenna to the K2 (or any
>>other radio), then a preamp will help.
>>If there *is* a noise increase when the antenna is connected, then
>>*usually* a preamp will not help - it will make the atmospheric
>>noise heard in the audio output greater, but that is not a signal -
>>we normally do not copy signals buried in the atmospheric noise -
>>although a few ops have excellent ears for doing just that.
>>Warren & Barbara Reese wrote:
>>>Dear fellow Elecrafters,
>>>
>>>I want to report the stunning success the PT-3 has had on the
>>>upper bands. Especially 15 and 10 meters. I have long held the
>>>suspicion that the K2 is deficient in sensitivity on these bands
>>>and the PT-3 confirms it in spades. Stations that are
>>>indecipherable now stand out clearly in arm chair copy.
>>>
>>>Let me recommend to others to try the PT-3 !
>>>
>>>BTW, my K2 has been back to both Gary and Don and has been checked
>>>on the higher bands for sensitivity. It has returned both times
>>>with a testimonial as to it's being OK.
>>>
>>>TR, K6GC, the Great Circle Station
>>>in the State of Jefferson.
>>>http://www.ijpr.org/Page.asp?NavID=1033
>>>
>>>K2/100/KAT S/N 838, Updated with all the new mods.

W8JI

Re: Ameco PT-3

> When the antenna is connected and disconnected the noise floor moves just
> barely. You can tell, but it requires a critical ear.

That is too little. That is about how my K3 behaves on six meters on SSB
bandwidth! On the narrowest bandwidth you use, you should hear a very well
defined noise increase, several dB, going from a dummy load to the antenna.

>>A note about my antenna. It is a HyGain 5BDQ trap dipole and the SWR on
>>it is 1.2:1 into about 200' of LMR240.

Since feedline loss and SWR in receiving is set by the receiver, SWR in the
feedline on receive has nothing to do with transmit VSWR (where the antenna
is the load). I've never measured the input impedance of the K2, but it
could be you have an impedance mismatch between the K2 receiver and the
feedline, which would result in feedline losses aggravating the feedline
loss problem.

What the 1.2:1 SWR indicates is the antenna mismatch is around 1.4:1 and
feedline loss on transmitting is about 2.5 dB.

I have no idea what the K2 looks like for SWR on receiving, but many
receivers I've measured are pretty far off 1:1 SWR. If the K2 looks like a
2.5:1 SWR (which is a reasonable upper limit based on other receivers I have
tested), feedline loss would be 3 dB plus you would have an additional .12
dB mismatch loss at the antenna (the source).

Sounds to me like the K2 you have needs more sensitivity if a dipole with 4
dB or less system loss won't firmly set noise floor.

73 Tom

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TR K2 #838

Re: Ameco PT-3

In reply to this post by TR K2 #838

Tom,

Thanks for your comments.

I appreciate your taking the time to answer my posting. I have great
admiration for you, having been in the 'biz most of my life
www.radions.net/comrcial.htm .

73.

TR, K6GC, the Great Circle Station
in the State of Jefferson.
http://www.ijpr.org/Page.asp?NavID=1033
____________________________________________
At 09:58 AM 7/12/2010 -0400, you wrote:

>>When the antenna is connected and disconnected the noise floor
>>moves just barely. You can tell, but it requires a critical ear.
>
>That is too little. That is about how my K3 behaves on six meters on
>SSB bandwidth! On the narrowest bandwidth you use, you should hear a
>very well defined noise increase, several dB, going from a dummy
>load to the antenna.
>
>>>A note about my antenna. It is a HyGain 5BDQ trap dipole and the
>>>SWR on it is 1.2:1 into about 200' of LMR240.
>
>Since feedline loss and SWR in receiving is set by the receiver, SWR
>in the feedline on receive has nothing to do with transmit VSWR
>(where the antenna is the load). I've never measured the input
>impedance of the K2, but it could be you have an impedance mismatch
>between the K2 receiver and the feedline, which would result in
>feedline losses aggravating the feedline loss problem.
>
>What the 1.2:1 SWR indicates is the antenna mismatch is around 1.4:1
>and feedline loss on transmitting is about 2.5 dB.
>
>I have no idea what the K2 looks like for SWR on receiving, but many
>receivers I've measured are pretty far off 1:1 SWR. If the K2 looks
>like a 2.5:1 SWR (which is a reasonable upper limit based on other
>receivers I have tested), feedline loss would be 3 dB plus you would
>have an additional .12 dB mismatch loss at the antenna (the source).
>
>Sounds to me like the K2 you have needs more sensitivity if a dipole
>with 4 dB or less system loss won't firmly set noise floor.
>
>73 Tom