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sub receiver question

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Jim Danehy-3

sub receiver question

I own K3 # 3355. Love it. Only thing I do not have is the digital recorder and the sub receiver. I am considering the sub receiver. I read in the operating manual that there is a -3 db loss when both receivers are using the "splitter" (common antenna). Is that interpretation correct ? I would probably not be using two antennas except on 160 and 80 which I operate sparingly in the winter. If I use the sub receiver and the main receiver from the same antenna can you notice the -3 db loss ? As we know that is a halving of the signal. One db is the lowest difference your ear can detect.

Jim W9VNE
K2 & K3 owner
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Bill W4ZV

Re: sub receiver question

jim danehy wrote

I own K3 # 3355. Love it. Only thing I do not have is the digital recorder and the sub receiver. I am considering the sub receiver. I read in the operating manual that there is a -3 db loss when both receivers are using the "splitter" (common antenna). Is that interpretation correct ? I would probably not be using two antennas except on 160 and 80 which I operate sparingly in the winter. If I use the sub receiver and the main receiver from the same antenna can you notice the -3 db loss ? As we know that is a halving of the signal. One db is the lowest difference your ear can detect.

Yes there's a 3 dB loss because the signal is split into two. On the low bands, you will never notice a 3 dB loss because the ambient noise is so far above the K3's sensitivity.

73, Bill

Dick Dievendorff

Re: sub receiver question

In reply to this post by Jim Danehy-3

Jim: I don't even notice it. The noise is similarly halved, so I just
turn the gain to a comfortable level. The "loss" is that half the
signal is going to each receiver.

Others can explain it more technically, but I don't notice this "loss"

Dick, K6KR

Sent from my iPhone

On Oct 16, 2009, at 4:12 PM, "Jim Danehy" <[hidden email]> wrote:

> I own K3 # 3355. Love it. Only thing I do not have is the digital
> recorder and the sub receiver. I am considering the sub receiver. I
> read in the operating manual that there is a -3 db loss when both
> receivers are using the "splitter" (common antenna). Is that
> interpretation correct ? I would probably not be using two antennas
> except on 160 and 80 which I operate sparingly in the winter. If I
> use the sub receiver and the main receiver from the same antenna can
> you notice the -3 db loss ? As we know that is a halving of the
> signal. One db is the lowest difference your ear can detect.
>
> Jim W9VNE
> K2 & K3 owner
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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wayne burdick

Re: sub receiver question

Administrator

In reply to this post by Jim Danehy-3

Jim Danehy wrote:

> I own K3 # 3355. Love it. Only thing I do not have is the digital
> recorder and the sub receiver. I am considering the sub receiver. I
> read in the operating manual that there is a -3 db loss when both
> receivers are using the "splitter" (common antenna). Is that
> interpretation correct ? I would probably not be using two antennas
> except on 160 and 80 which I operate sparingly in the winter. If I
> use the sub receiver and the main receiver from the same antenna can
> you notice the -3 db loss ? As we know that is a halving of the
> signal. One db is the lowest difference your ear can detect.

Hi Jim,

This is correct. Virtually all true dual-receive implementations use a
3-dB splitter to route the signal to both receivers while preserving
impedance match.

Most of the time you won't notice the 3 dB loss. It would only come
into play on a band where both the noise and signals are extremely
weak, and if it's an issue, you can turn the sub receiver off or use a
separate antenna.

You'll want a separate antenna anyway so you can use diversity
receive, which works amazingly well in fading conditions. 160 and 80
meter operators in particular use this technique.

I'd suggest matching the crystal filters on the main and sub
receivers, at least those you might be using for diversity receive.

73,
Wayne
N6KR

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N5GE

Re: sub receiver question

In reply to this post by Bill W4ZV

On Fri, 16 Oct 2009 16:17:18 -0700 (PDT), Bill W4ZV
<[hidden email]> wrote:

>
>
>
>jim danehy wrote:
>>
>> I own K3 # 3355. Love it. Only thing I do not have is the digital recorder
>> and the sub receiver. I am considering the sub receiver. I read in the
>> operating manual that there is a -3 db loss when both receivers are using
>> the "splitter" (common antenna). Is that interpretation correct ? I would
>> probably not be using two antennas except on 160 and 80 which I operate
>> sparingly in the winter. If I use the sub receiver and the main receiver
>> from the same antenna can you notice the -3 db loss ? As we know that is a
>> halving of the signal. One db is the lowest difference your ear can
>> detect.
>>
>
>Yes there's a 3 dB loss because the signal is split into two. On the low
>bands, you will never notice a 3 dB loss because the ambient noise is so far
>above the K3's sensitivity.
>
>73, Bill

Bill is correct about probably not noticing the difference, but if it
bothers you, you have the option of turning each receiver's preamp on.

73,

Tom, N5GE

[hidden email]
K3 #806, K3 #1055, PR6,
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paulb

Re: sub receiver question

In reply to this post by Jim Danehy-3

3dB accross the combiner using both recievers, for low band use not an issue.

The digi audio recorder is great. On air play-back is excellent.

cheers

Paul
zl1ajy

<quote author="jim danehy">
I own K3 # 3355. Love it. Only thing I do not have is the digital recorder and the sub receiver. I am considering the sub receiver. I read in the operating manual that there is a -3 db loss when both receivers are using the "splitter" (common antenna). Is that interpretation correct ? I would probably not be using two antennas except on 160 and 80 which I operate sparingly in the winter. If I use the sub re

Mike Harris

Re: sub receiver question

In reply to this post by Jim Danehy-3

G'day,

A contrary opinion, yes it is noticeable, particularly when trying
to work signals near the noise. I usually have to crack where the
callers are going through and then toggle the sub-RX off to make
sure I have good copy on the target. In some circumstances I still
find that using REV is the better option. Naturally if the target
is head and shoulders above the noise, no problem, and the sub-RX
sure makes working split a treat.

Regards,

Mike VP8NO
K2 #1400
K3 #345

----- Original Message -----
From: "Jim Danehy" <[hidden email]>
To: "Elecraft Reflector" <[hidden email]>
Sent: Friday, October 16, 2009 8:12 PM
Subject: [Elecraft] sub receiver question

Bill Steffey NY9H

Re: sub receiver question... 3db loss w/ 2 rcvrs

In reply to this post by paulb

I heard an ICOM employee explain that the 7700 was better than the
7800 because the 7700 did not have the 3db loss ... because it only
had one receiver in the 7700 !!!!!.... wow ..that must make it a
"contest set" .

i certainly don't mind the split loss in the 7800 or the k3......

I had installed one in my 756pro3,,,, so i could have a real 2nd receiver.....
and actually use a minicircuits in the K3 IF out so I can feed both
my LP-PAn & the SDR/IQ...
I like rocky on the LPpan....

bill

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Ross Primrose N4RP

Re: sub receiver question... 3db loss w/ 2 rcvrs

Bill NY9H wrote:
> I heard an ICOM employee explain that the 7700 was better than the
> 7800 because the 7700 did not have the 3db loss ... because it only
> had one receiver in the 7700 !!!!!.... wow ..that must make it a
> "contest set" .
>
> i certainly don't mind the split loss in the 7800 or the k3......
> lease help support this email list: http://www.qsl.net/donate.html
>
The 3dB loss is meaningless. All modern receivers have way more
sensitivity than they need....

73, Ross N4RP

--
FCC Section 97.313(a) “At all times, an amateur station must use the minimum transmitter power necessary to carry out the desired communications.”

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Johnny Siu

Re： sub receiver question... 3db loss w/ 2 rcvrs

Hi Ross,

The statement from the "icom employee" is correct NOT because of the insertion loss. IC7700 used a newer version DSP IC. If you have the chance to do an A/B comparison between IC7800 and IC7700 using same antenna, you will notice that the IC7700's receiver is marginally quieter than IC7800. However, in day-to-day operation, it is difficult to notice that.

The successfulness of DSP will depend on :

1. the speed / specification of the DSP IC;
2. the skill of writing the DSP firmware

In other words, even both rigs use the same DSP ICs, the difference could be day and night if the DSP firmware has been poorly written. No doubt, through the frequent updates of the K3 firmware, I experience the improvements of NR in K3 which are good to our Elecrafters.

73

Johnny Siu VR2XMC

K3, K2s

________________________________
寄件人﹕ Ross Primrose <[hidden email]>
副本(CC) [hidden email]
傳送日期﹕ 2009/11月/3 (二) 2:11:10 PM
主題： Re: [Elecraft] sub receiver question... 3db loss w/ 2 rcvrs

Bill NY9H wrote:
> I heard an ICOM employee explain that the 7700 was better than the
> 7800 because the 7700 did not have the 3db loss ... because it only
> had one receiver in the 7700 !!!!!.... wow ..that must make it a
> "contest set" .
>
> i certainly don't mind the split loss in the 7800 or the k3......
> lease help support this email list: http://www.qsl.net/donate.html
>
The 3dB loss is meaningless. All modern receivers have way more
sensitivity than they need....

73, Ross N4RP

Yahoo!香港提供網上安全攻略，教你如何防範黑客! 請前往 http://hk.promo.yahoo.com/security/ 了解更多!
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