[Elecraft] K3 6-meter Performance Question

[Brian Alsop]

Ian,

One also needs perhaps 10db of noise "headroom" for modes like JT65 
which copy many db below the noise.
My opinion is the an internal option for this preamp is needed.  
Dangling still another box  with the attendent extra cables outside the 
K3 isn't desirable here.  Yes the preamp does handle the LF rx antenna-- 
still more complication.

Perhaps Elecraft can come up with both an internal and external fix and 
let the market decide.   I'd like nothing better than pushing the preamp 
button and getting a souped up 6M preamp without more external junk.  

However Elecraft knows the guts of the K3 and perhaps an internal fix 
isn't practical.  At least it would be nice to know that.

Of course the best place for a preamp is at the antenna.  However, the 
problems that generates when one is running high power introduces even 
more complexity.

73 de Brian/K3KO


Ian White GM3SEK wrote:

> On Tuesday, Dick K5AND wrote:
>
>> Ciao, from CY0X, Sable Island.....
>
> [...]
>
>>
>> Since it is so easy to switch out the outboard preamp, we have 
>> frequently
>> done this on some of the weak sigs just to see if we could still hear 
>> them.
>> In many cases we could hear them Q5 with just the internal preamp. Ian,
>> GM3SEK, et al, have pointed out that the stock radio NF is somewhere 
>> in the
>> 8-10db range, which is not stellar as six meter radio specs go. 
>> Nonetheless,
>> you'd be surprised at how many weak sigs we can still hear with only the
>> internal preamp engaged.
>>
> That's not surprising at all, as the K3 is only slightly lacking in 
> sensitivity on 6m. But contrary to other reports from users in very 
> quiet sites, my stock K3 can NOT hear background noise at 50MHz.
>
> Before making that statement, I took a couple of days to confirm that 
> nothing else is wrong with the system. Receiver sensitivity meets 
> Elecraft's 'typical' specification with a few dB to spare. Feeder loss 
> was re-measured. And above all, I re-confirmed that my old IC-746 CAN 
> hear background noise from the same antenna/feedline with a 
> comfortable 3-5dB margin.
>
> A good operator like Dick can often make up for a few dB lacking in 
> signal/noise ratio... but only at the expense of greater operator 
> fatigue, and with the knowledge that some marginal QSOs *will* be 
> lost, when a more sensitive receiver could have pulled them through. 
> That is precisely why the receiver at CY0X has a prototype Elecraft 
> preamp.
>
> One small correction: Elecraft's specification for a typical MDS 
> (noise floor) of -136dBm in a noise bandwidth of 500Hz corresponds to 
> a noise figure of about 13dB (significantly more than 8-10dB). Cutting 
> through the technicalities, at a genuinely quiet 6m site that deficit 
> *is* noticeable - a gap in the K3's otherwise all-round excellence.
>
>


Ian White GM3SEK wrote:

> On Tuesday, Dick K5AND wrote:
>
>> Ciao, from CY0X, Sable Island.....
>
> [...]
>
>>
>> Since it is so easy to switch out the outboard preamp, we have 
>> frequently
>> done this on some of the weak sigs just to see if we could still hear 
>> them.
>> In many cases we could hear them Q5 with just the internal preamp. Ian,
>> GM3SEK, et al, have pointed out that the stock radio NF is somewhere 
>> in the
>> 8-10db range, which is not stellar as six meter radio specs go. 
>> Nonetheless,
>> you'd be surprised at how many weak sigs we can still hear with only the
>> internal preamp engaged.
>>
> That's not surprising at all, as the K3 is only slightly lacking in 
> sensitivity on 6m. But contrary to other reports from users in very 
> quiet sites, my stock K3 can NOT hear background noise at 50MHz.
>
> Before making that statement, I took a couple of days to confirm that 
> nothing else is wrong with the system. Receiver sensitivity meets 
> Elecraft's 'typical' specification with a few dB to spare. Feeder loss 
> was re-measured. And above all, I re-confirmed that my old IC-746 CAN 
> hear background noise from the same antenna/feedline with a 
> comfortable 3-5dB margin.
>
> A good operator like Dick can often make up for a few dB lacking in 
> signal/noise ratio... but only at the expense of greater operator 
> fatigue, and with the knowledge that some marginal QSOs *will* be 
> lost, when a more sensitive receiver could have pulled them through. 
> That is precisely why the receiver at CY0X has a prototype Elecraft 
> preamp.
>
> One small correction: Elecraft's specification for a typical MDS 
> (noise floor) of -136dBm in a noise bandwidth of 500Hz corresponds to 
> a noise figure of about 13dB (significantly more than 8-10dB). Cutting 
> through the technicalities, at a genuinely quiet 6m site that deficit 
> *is* noticeable - a gap in the K3's otherwise all-round excellence.
>
>