Re: Topband: Front End Filters

[Rudy Bakalov via Topband]

This is the original ask:

"What if we take it a step further, could we limit the band-with of the antenna 
signal with a crystal lattice for 160 meters before the receiver. 
Years ago I played  around with a single crystal at the input of an old tube 
type receiver. It was remarkable what I could hear on 40 meters, on what seemed 
to be one frequency."
I understand the proposed solution- and have used one on 80- but fail to 
understand the problem statement in the year 2017. Crystal from ends, Q 
multipliers, etc. existed at a time when RX antennas were not common and radios 
had poor performance. And yes, they worked really well and turned rigs like the 
TS530 and Heathkit SB 102/104 into amazing receivers. Personally, I will never 
go back to one of these solutions.
What I did find surprisingly effective is a good set of BPFs. Using a QS1R SDR 
I observed a material reduction of band noise, including on 20 m, at my remote 
VE3 location, which is already amazingly quiet. Ditto for the Icom 7300 which 
became an even greater pleasure to use with a set of BPFs in front of it.
Rudy N2WQ

Sent using a tiny keyboard.  Please excuse brevity, typos, or inappropriate 
autocorrect.


> On Dec 24, 2016, at 9:40 AM, K1FZ-Bruce  wrote:
> 
> Rudy,
>  
> Using topband archives.  Try going back to the beginninmg of the emails. It 
> started with "thinking out loud", subject then someone changed the subject.
>  
> 73' Bruce-k1fz
>  
>  
> 
> On Sat, 24 Dec 2016 08:46:47 -0500, Rudy Bakalov via Topband 
>  wrote:
> So what problem are we trying to solve here?
> 
> 
> 73, Rudy N2WQ
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Re: Topband: Front End Filters

[K1FZ-Bruce]

Rudy,
 
Using topband archives.  Try going back to the beginninmg of the 
emails. It started with "thinking out loud", subject then someone 
changed the subject. 


 
73' Bruce-k1fz
 
 

On Sat, 24 Dec 2016 08:46:47 -0500, Rudy Bakalov via Topband  wrote:

  So what problem are we trying to solve here?

73, Rudy N2WQ


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Re: Topband: Front End Filters

[Rudy Bakalov via Topband]

So what problem are we trying to solve here?

If we are solving for SNR, IMHO, good RX antennas provide the best bang for the 
buck.  Today's RX antennas are built on sound engineering principles, have 
measurable performance, and offer operating flexibility a crystal front-end 
can't.

If we are improving selectivity, I wonder if we are beyond the point of 
diminishing returns. There are many modern radios that have performance beyond 
what's needed during a contest. Further, during a contest, it is key clicks or 
splatter that cause the greatest pain; how can the crystal front-end alleviate 
the impact of such garbage?

Wishing everyone a happy holidays season.

73, Rudy N2WQ

Sent using a tiny keyboard.  Please excuse brevity, typos, or inappropriate 
autocorrect.


> On Dec 24, 2016, at 12:48 AM, K1FZ-Bruce  wrote:
> 
>  
> The one they are  developing for marketing 'can' have 1 KHZ segment crystals 
> channels..  
> I would encourage anyone to insert a single crystal in their receiver antenna 
> input to see the
> difference before considering a purchase.  (Careful not to transmit into the 
> experiement)
> 40 meters is a good test  band as usually has many signals after dark..  
> 73
> Bruce-k1fz
>  
>  
> 
> On Fri, 23 Dec 2016 17:56:07 -0700, Dave  wrote:
> 
>  About 15 years ago I built a switchable front end crystal filter, I was
> going to market it but it was too expensive for the Ham market. It covers
> 1800 to 1850 in 5kHz segments with a slight overlap so that there are no
> gaps, each section is a half lattice, the insertion loss is about 6dB but
> that isn't a problem because I always have about -15dB of attenuation in the
> receive path input. Nose bandwidth is 5kHz and about 8kHz at -20dB. Lack of
> noise blanker performance is not a problem because big signals make the
> blanker useless anyway. I used it during contests when my rig was an IC781,
> since changing to a more modern rig, an IC7851, the filter provides no
> significant improvement. For working DX on a crowded band it is useful if
> your rig does not have a good roofing filter. 
> HNY /MX
> 
> Dave AA0RS
> 
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> Topband Reflector Archives - http://www.contesting.com/_topband
> 
> 
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Re: Topband: Front End Filters

[Raoul Coetzee via Topband]

surely it is important to have the correct loading on the crystal,  just 
connecting a crystal in the antenna path is not so good?It seems good loading 
is around 1-3k.
Merry Christmas to all.Raoul ZS1C 



  From: K1FZ-Bruce <k...@myfairpoint.net>
 To: topband@contesting.com; Dave <rfsa...@freng.com> 
 Sent: Saturday, December 24, 2016 7:48 AM
 Subject: Topband: Front End Filters
   
 
The one they are  developing for marketing 'can' have 1 KHZ segment 
crystals channels.. 
 
I would encourage anyone to insert a single crystal in their receiver 
antenna input to see the
difference before considering a purchase.  (Careful not to transmit 
into the experiement)
40 meters is a good test  band as usually has many signals after dark.. 
 
73
Bruce-k1fz
 
 

On Fri, 23 Dec 2016 17:56:07 -0700, Dave  wrote:

      About 15 years ago I built a switchable front end crystal filter, I was
going to market it but it was too expensive for the Ham market. It covers
1800 to 1850 in 5kHz segments with a slight overlap so that there are no
gaps, each section is a half lattice, the insertion loss is about 6dB but
that isn't a problem because I always have about -15dB of attenuation in the
receive path input. Nose bandwidth is 5kHz and about 8kHz at -20dB. Lack of
noise blanker performance is not a problem because big signals make the
blanker useless anyway. I used it during contests when my rig was an IC781,
since changing to a more modern rig, an IC7851, the filter provides no
significant improvement. For working DX on a crowded band it is useful if
your rig does not have a good roofing filter. 

HNY /MX

Dave AA0RS

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Topband: Front End Filters

[K1FZ-Bruce]

 
The one they are  developing for marketing 'can' have 1 KHZ segment 
crystals channels.. 
 
I would encourage anyone to insert a single crystal in their receiver 
antenna input to see the
difference before considering a purchase.  (Careful not to transmit 
into the experiement)
40 meters is a good test  band as usually has many signals after dark.. 
 

73
Bruce-k1fz
 
 

On Fri, 23 Dec 2016 17:56:07 -0700, Dave  wrote:

  About 15 years ago I built a switchable front end crystal filter, I was
going to market it but it was too expensive for the Ham market. It covers
1800 to 1850 in 5kHz segments with a slight overlap so that there are no
gaps, each section is a half lattice, the insertion loss is about 6dB but
that isn't a problem because I always have about -15dB of attenuation in the
receive path input. Nose bandwidth is 5kHz and about 8kHz at -20dB. Lack of
noise blanker performance is not a problem because big signals make the
blanker useless anyway. I used it during contests when my rig was an IC781,
since changing to a more modern rig, an IC7851, the filter provides no
significant improvement. For working DX on a crowded band it is useful if
your rig does not have a good roofing filter. 


HNY /MX

Dave AA0RS

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Topband: Front End Filters

[Dave]

About 15 years ago I built a switchable front end crystal filter, I was
going to market it but it was too expensive for the Ham market. It covers
1800 to 1850 in 5kHz segments with a slight overlap so that there are no
gaps, each section is a half lattice, the insertion loss is about 6dB but
that isn't a problem because I always have about -15dB of attenuation in the
receive path input. Nose bandwidth is 5kHz and about 8kHz at -20dB.  Lack of
noise blanker performance is not a problem because big signals make the
blanker useless anyway. I used it during contests when my rig was an IC781,
since changing to a more modern rig, an IC7851, the filter provides no
significant improvement. For working DX on a crowded band it is useful if
your rig does not have a good roofing filter.

 

HNY /MX

 

Dave AA0RS

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