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K3 on 6

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Ron Spencer

K3 on 6

Anyone else notice (and I know this will be difficult with hardly any
openings) that the sensitivity of the K3 on 6 is down? Compared to the 746 I
have it seems down quite a bit (even with the K3 preamp on).

Will be interested to hear what others have to say. Can report off list
([hidden email]) and I can summarize for posting.

Thanks
Ron
N4XD

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wayne burdick

Re: K3 on 6 m: the external low-noise preamp project

Administrator

Ron Spencer wrote:

> Anyone else notice (and I know this will be difficult with hardly any
> openings) that the sensitivity of the K3 on 6 is down? Compared to the
> 746 I
> have it seems down quite a bit (even with the K3 preamp on).

Ron,

The K3 is optimized for high dynamic range. For example, it has 40 dB
higher blocking dynamic range and 25 to 30 dB higher IMDDR3 than the
IC746. It also has narrow ham-band filters, and the one for 6 meters is
triple-tuned, having about 1 to 2 dB higher loss than a double-tuned
filter.

The IC746 *does* have a low-noise second preamp that is often used on 6
meters, improving MDS to around -142 dBm (from the QST review). To
achieve an MDS this good on 6 meters in the K3 -- with its narrow
band-pass filters -- requires a preamp at a different point in the
signal path: inserted between RX ANT IN and OUT. This bypasses other
loss sources including the KAT3, low-pass filters, and T-R switch.

We've designed a dedicated 6-m preamp for this purpose. It's very
small, and has its connectors spaced so it can be directly connected to
RX ANT IN/OUT. Measured MDS on 6-m with the preamp patched in is around
-142 to -143 dBm. It can be switched in automatically on 6 m only by
the K3. It also includes a bypass relay so you can still use a receive
antenna for other bands.

I'm not sure when the new preamp will available. But if you're
interested in field testing one, please send me an e-mail.

tnx
Wayne
N6KR

---

http://www.elecraft.com

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Stewart Baker

Re: K3 on 6

In reply to this post by Ron Spencer

Hi Ron,
This issue has been noted and discussed before. My K3 is very deaf
compared with my previous 6m setup of a K2 and KXV50.

The bottom line is that the K3 receive performance has been
optimised to cope with strong signals below 30MHz. To achieve an
adequate sensitivity on 6m you either need to make or buy an
external pre-amp.

Elecraft have designed one, but it is not released yet. You will
also need the KXV3 interface option, unless you make very sure
that you are not going to accidentally transmit into the pre-amp.
In addition this solution adds extra external wiring complexity.

73
Stewart G3RXQ
On Wed, 14 May 2008 11:51:58 -0400, Ron Spencer wrote:
> Anyone else notice (and I know this will be difficult with
hardly any
> openings) that the sensitivity of the K3 on 6 is down? Compared
to the 746 I
> have it seems down quite a bit (even with the K3 preamp on).
>
> Will be interested to hear what others have to say. Can report
off list

> ([hidden email]) and I can summarize for posting.
>
> Thanks
> Ron
> N4XD
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com

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Stewart Baker

Re: K3 on 6

Sorry,
I should have added that the wiring complexity is increased if you
wish to use the pre-amp with an HF receive antenna.

73
Stewart G3RXQ
On Wed, 14 May 2008 17:24:16 +0100, Stewart Baker wrote:
> Hi Ron,
> This issue has been noted and discussed before. My K3 is very
deaf

> compared with my previous 6m setup of a K2 and KXV50.
>
> The bottom line is that the K3 receive performance has been
> optimised to cope with strong signals below 30MHz. To achieve an
> adequate sensitivity on 6m you either need to make or buy an
> external pre-amp.
>
> Elecraft have designed one, but it is not released yet. You will
> also need the KXV3 interface option, unless you make very sure
> that you are not going to accidentally transmit into the

pre-amp.

> In addition this solution adds extra external wiring complexity.
>
> 73
> Stewart G3RXQ
> On Wed, 14 May 2008 11:51:58 -0400, Ron Spencer wrote:
>> Anyone else notice (and I know this will be difficult with
> hardly any
>> openings) that the sensitivity of the K3 on 6 is down? Compared
> to the 746 I
>> have it seems down quite a bit (even with the K3 preamp on).
>>
>> Will be interested to hear what others have to say. Can report
> off list
>> ([hidden email]) and I can summarize for posting.
>>
>> Thanks
>> Ron
>> N4XD
>>
>> _______________________________________________
>> Elecraft mailing list
>> Post to: [hidden email]
>> You must be a subscriber to post to the list.
>> Subscriber Info (Addr. Change, sub, unsub etc.):
>> http://mailman.qth.net/mailman/listinfo/elecraft
>>
>> Help: http://mailman.qth.net/subscribers.htm
>> Elecraft web page: http://www.elecraft.com
>>
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
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>
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> Elecraft web page: http://www.elecraft.com

Brendan Minish

Re: K3 on 6

In reply to this post by Ron Spencer

Hello Ron,

It's got less gain than my 7800 but I can still hear about 2dB more
noise on my antenna than I can on a 50 Ohm load.

I do 6m EME on occasion and I have been successful in monitoring 6m EME
QSOs with the K3, so for my setup (7 ele long yagi, Quiet rural area,
low loss feeder ) the limiting factor is band noise not RX noise or lack
of K3 sensitivity.

For others they may need more gain but in general if your antenna is
noisier than a 50 Ohm load then you have enough system gain, more gain
is unlikely to help as it will bring up the noise right along with the
desired signals

Elecraft are planning a 6m preamp to go with the K3 in any case

73
Brendan EI6IZ K3 #39

On Wed, 2008-05-14 at 11:51 -0400, Ron Spencer wrote:
> Anyone else notice (and I know this will be difficult with hardly any
> openings) that the sensitivity of the K3 on 6 is down? Compared to the 746 I
> have it seems down quite a bit (even with the K3 preamp on).
>
> Will be interested to hear what others have to say. Can report off list
> ([hidden email]) and I can summarize for posting.

--
Don‘t complain. Nobody will understand. Or care. And certainly don‘t try
to fix the situation yourself. It‘s dangerous. Leave it to a highly
untrained, unqualified, expendable professional.

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Bill Churchill

Re: K3 on 6

I have the same experience here with my 5 element beam.
The K3 receives better on 6m than my home made transverter that I used on 6
with the K2. In general I have trouble working weak stations anyway. Perhaps
more power out would make it better -
-Bill Churchill
AA1O
K3 287
K2 1740
----- Original Message -----
From: "Brendan Minish" <[hidden email]>
To: "Ron Spencer" <[hidden email]>
Cc: "Elecraft" <[hidden email]>
Sent: Wednesday, May 14, 2008 3:27 PM
Subject: Re: [Elecraft] K3 on 6

> Hello Ron,
>
> It's got less gain than my 7800 but I can still hear about 2dB more
> noise on my antenna than I can on a 50 Ohm load.
>
> I do 6m EME on occasion and I have been successful in monitoring 6m EME
> QSOs with the K3, so for my setup (7 ele long yagi, Quiet rural area,
> low loss feeder ) the limiting factor is band noise not RX noise or lack
> of K3 sensitivity.
>
> For others they may need more gain but in general if your antenna is
> noisier than a 50 Ohm load then you have enough system gain, more gain
> is unlikely to help as it will bring up the noise right along with the
> desired signals
>
> Elecraft are planning a 6m preamp to go with the K3 in any case
>
> 73
> Brendan EI6IZ K3 #39
>
> On Wed, 2008-05-14 at 11:51 -0400, Ron Spencer wrote:
>> Anyone else notice (and I know this will be difficult with hardly any
>> openings) that the sensitivity of the K3 on 6 is down? Compared to the
>> 746 I
>> have it seems down quite a bit (even with the K3 preamp on).
>>
>> Will be interested to hear what others have to say. Can report off list
>> ([hidden email]) and I can summarize for posting.
>
> --
> Don‘t complain. Nobody will understand. Or care. And certainly don‘t try
> to fix the situation yourself. It‘s dangerous. Leave it to a highly
> untrained, unqualified, expendable professional.
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
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>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com

Gary Hembree

Re: K3 on 6

In reply to this post by Ron Spencer

Ron et al,
Compared to my XV50/K2 station my K3 is much more practical on 6 meters in a suburban, high noise, high EMI environment (metro Phoenix). The attenuator had to be always on in my K2 to keep it from being overloaded by the XV50 RX output. In addition I turned the K2 RF gain down to bring the system gain down to improve the audio S/N. To use the XV50 at all here, because of internally generated IMD products, I had to build a N6CA terminating high pass/low pass filter to put in the antenna lead to filter out the multiple hundreds of kilowatts worth of FM and TV carriers that are being transmitted 10 miles LOS from my QTH.

I have had no such difficulties with the K3. With my 7/8 wavelength, 5 element Yagi at 45' I have heard plenty of MS pings and bursts and all of the usual tropo signals that I am used to hearing and working within 120 miles of here in mountainous central Arizona. The sensitivity to dynamic range balance seems fine to me on the K3 as is. Any further decreases in noise figure should be done with a low-gain external preamp at or near the antenna.
(See N6CA's web site for information on the terminating low pass filter and an excellent VHF preamp.)

73
Gary, N7IR
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