Topics

BCI filter question.

KG5NII
 

I am thinking seriously about experimenting with the uBitX but am wondering in advance if someone could suggest  a good broadcast band filter I can build that is known to be effective. I live less than 1 mile (1.6 km) from a 50 kW AM broadcast station transmitting on 1180 kHz. I know this will be a problem with on the uBitX as even on mid, high end commercial ham rigs I get significant interference on 3540, 7040, 14160 kHz and so on.   In fact, I'd probably want to build an additional one for my Yaesu.  I know there are a lot of circuits out there for BCI filters but that doesn't necessarily mean they are or would be effective.  Cost is a major concern,  and commercial filter units seem to be rather pricey, but on the other hand, purchasing the components, etc may not necessarily be cost effective either given the somewhat high cost of shipping and given that  not everything could necessarily be purchased from one place, thereby rising costs even more.    I'd probably want to build one for the uBitX and one for my 100W Yaesu  just to give it over and done with.  There is not a day that goes by that I do not wish the four AM 1180 transmitter  towers down the road from me  are flattened by a tornado until I realize that would only be a temporary reprieve at best  but building, installing some good filters will be a permanent one.  


So advice please.


Thanks.

Ron, KG5NII



Gordon Gibby <ggibby@...>
 

so....that sounds like even with harmonic suppression, you have SIGNIFICANT energy coming at your on the harmonics of their primary frequency.....


hopefullly it ISNT being created within some nonlinear junction in your own radio....the way to prevent that would be a high pass filter in your transmission line designed to pass anything above, say 2 MHz and not pass stuff below that.    I'm guessing you already have those kinds of filters?


beyond that, the actual hamonic radiated energy generated by THEIR TRANSMITTER  is a fact of life, and you aren't going to be able to receive much (other than them) on those frequencies....


if you try and builld a notch filter (high Q, narrow bandwidth) for each of their harmonics youll hear them less....but you'll also hear other people near those frequencies less also....





From: BITX20@groups.io <BITX20@groups.io> on behalf of KG5NII <kg5nii@...>
Sent: Tuesday, January 2, 2018 8:52 AM
To: BITX20@groups.io
Subject: [BITX20] BCI filter question.
 

I am thinking seriously about experimenting with the uBitX but am wondering in advance if someone could suggest  a good broadcast band filter I can build that is known to be effective. I live less than 1 mile (1.6 km) from a 50 kW AM broadcast station transmitting on 1180 kHz. I know this will be a problem with on the uBitX as even on mid, high end commercial ham rigs I get significant interference on 3540, 7040, 14160 kHz and so on.   In fact, I'd probably want to build an additional one for my Yaesu.  I know there are a lot of circuits out there for BCI filters but that doesn't necessarily mean they are or would be effective.  Cost is a major concern,  and commercial filter units seem to be rather pricey, but on the other hand, purchasing the components, etc may not necessarily be cost effective either given the somewhat high cost of shipping and given that  not everything could necessarily be purchased from one place, thereby rising costs even more.    I'd probably want to build one for the uBitX and one for my 100W Yaesu  just to give it over and done with.  There is not a day that goes by that I do not wish the four AM 1180 transmitter  towers down the road from me  are flattened by a tornado until I realize that would only be a temporary reprieve at best  but building, installing some good filters will be a permanent one.  


So advice please.


Thanks.

Ron, KG5NII



Karl Heinz Kremer, K5KHK
 

For a cheap BCI filter, take a look here (it's the first article in this document): http://www.qrpforum.de/index.php?page=Attachment&attachmentID=16959&h=269da5721a0d272fc6ce550399700bfc9d9a8155

For a simpler, but slightly more expensive solution, see here: http://www.qrpme.com/?p=product&id=BCI

If you want something you can leave in during transmit, take a look here: http://vk3il.net/projects/broadcast-band-filter/

You an also calculate your own, all you need is a high-pass filter that cuts off just above the AM band. As Gordon suggested, a notch filter might be a good idea as well. 
--
Karl Heinz - K5KHK

Smitty, KR6ZY
 

I’ll add my design to the pile of other great (possibly better) options: 

Note that mine is only good for QRP power levels, or a receiver. 

-Mark

On Jan 2, 2018, at 6:28 AM, Karl Heinz Kremer, K5KHK <khk@...> wrote:

For a cheap BCI filter, take a look here (it's the first article in this document): http://www.qrpforum.de/index.php?page=Attachment&attachmentID=16959&h=269da5721a0d272fc6ce550399700bfc9d9a8155

For a simpler, but slightly more expensive solution, see here: http://www.qrpme.com/?p=product&id=BCI

If you want something you can leave in during transmit, take a look here: http://vk3il.net/projects/broadcast-band-filter/

You an also calculate your own, all you need is a high-pass filter that cuts off just above the AM band. As Gordon suggested, a notch filter might be a good idea as well. 
--
Karl Heinz - K5KHK

Dexter N Muir
 

I'm wondering: How about an anti-phase carrier to knock the guts out of each harmonic at appropriate levels? Phase-locked to fundamental with an output 'dirty' enough to have appropriate harmonics to knock the incoming energy for six. Filters then deal with sidebands if needed.
- Just off the top of the nut and ready to be shot down ... :)
73 de ZL2DEX

ohwenzelph
 

do you have to order 3 boards and what is the difference between selecting and not selecting 2 oz. copper?


Smitty, KR6ZY
 

They come in 3s, yes. Any multiple of three is a valid order quantity. This is an artifact of how they manufacture the boards. These boards are small enough and hence cheap enough it hopefully won’t be a problem. 

Don’t choose the 2oz copper. It’s a thicker copper on the board, but at also a thinner board. Probably not what you want. 

-Mark

On Jan 2, 2018, at 11:53 AM, ohwenzelph via Groups.Io <Ohwenzelph@...> wrote:

do you have to order 3 boards and what is the difference between selecting and not selecting 2 oz. copper?


K9HZ <bill@...>
 

You can build an excellent W3NQN BC filter for about $5. 


Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton - J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com


email:  bill@...

 


On Jan 2, 2018, at 7:52 AM, KG5NII <kg5nii@...> wrote:

I am thinking seriously about experimenting with the uBitX but am wondering in advance if someone could suggest  a good broadcast band filter I can build that is known to be effective. I live less than 1 mile (1.6 km) from a 50 kW AM broadcast station transmitting on 1180 kHz. I know this will be a problem with on the uBitX as even on mid, high end commercial ham rigs I get significant interference on 3540, 7040, 14160 kHz and so on.   In fact, I'd probably want to build an additional one for my Yaesu.  I know there are a lot of circuits out there for BCI filters but that doesn't necessarily mean they are or would be effective.  Cost is a major concern,  and commercial filter units seem to be rather pricey, but on the other hand, purchasing the components, etc may not necessarily be cost effective either given the somewhat high cost of shipping and given that  not everything could necessarily be purchased from one place, thereby rising costs even more.    I'd probably want to build one for the uBitX and one for my 100W Yaesu  just to give it over and done with.  There is not a day that goes by that I do not wish the four AM 1180 transmitter  towers down the road from me  are flattened by a tornado until I realize that would only be a temporary reprieve at best  but building, installing some good filters will be a permanent one.  


So advice please.


Thanks.

Ron, KG5NII



ohwenzelph
 

 K9HZ
Jan 2   

You can build an excellent W3NQN BC filter for about $5. “

Do do you have details on how?

K9HZ <bill@...>
 

If you search the QST archives for his call you will find two articles by him.  One for transmitting filters and one for receiving. The receiving filter document is the one you want.  These are the most common low pass/ band pass filters used by hams today.   


Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton - J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com


email:  bill@...

 


On Jan 3, 2018, at 3:35 AM, ohwenzelph via Groups.Io <Ohwenzelph@...> wrote:

 K9HZ
Jan 2   

You can build an excellent W3NQN BC filter for about $5. “

Do do you have details on how?

ohwenzelph
 

If you search the QST archives for his call”
not exactly details but helpful, with the $5 claim, I thought you might have something specific in mind
was it the feb 1978 bc band energy-a rejection filter
or
March 1983 

Alternative Filter Design
(Technical Correspondence)?
thanks


K9HZ <bill@...>
 

Sorry I'm sitting in a day long meeting with only a cell phone.  The W3NQN high pass and band pass filters work well and use 7 parts.  There is something else called a “brick wall AM” filter that was built by a guy in texas but i dont know much about it. 


Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton - J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com


email:  bill@...

 


On Jan 3, 2018, at 10:47 AM, ohwenzelph via Groups.Io <Ohwenzelph@...> wrote:

If you search the QST archives for his call”
not exactly details but helpful, with the $5 claim, I thought you might have something specific in mind
was it the feb 1978 bc band energy-a rejection filter
or
March 1983 

Alternative Filter Design
(Technical Correspondence)?
thanks


Vince Vielhaber
 

For those interested, that would be this one:

http://www.qsl.net/wb5wpa/Filter/AM%20Brick-Wall%20160%20Meter%20Filter.pdf

Vince.

On 01/03/2018 03:23 PM, K9HZ wrote:
Sorry I'm sitting in a day long meeting with only a cell phone. The
W3NQN high pass and band pass filters work well and use 7 parts. There
is something else called a “brick wall AM” filter that was built by a
guy in texas but i dont know much about it.


*Dr. **William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ
PJ2/K9HZ*



Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois



Owner – Operator

Villa Grand Piton - J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com <http://www.VillaGrandPiton.com>


email: @Doc_Bill <mailto:@Doc_Bill>




On Jan 3, 2018, at 10:47 AM, ohwenzelph via Groups.Io
<Ohwenzelph=yahoo.com@groups.io <mailto:Ohwenzelph=yahoo.com@groups.io>>
wrote:

“If you search the QST archives for his call”
not exactly details but helpful, with the $5 claim, I thought you
might have something specific in mind
was it the feb 1978 bc band energy-a rejection filter
or
March 1983


Alternative Filter Design
(Technical Correspondence)?
thanks

Vince Vielhaber
 

On 01/03/2018 03:49 PM, Vince Vielhaber wrote:
For those interested, that would be this one:

http://www.qsl.net/wb5wpa/Filter/AM%20Brick-Wall%20160%20Meter%20Filter.pdf

Vince.

On 01/03/2018 03:23 PM, K9HZ wrote:
Sorry I'm sitting in a day long meeting with only a cell phone. The
W3NQN high pass and band pass filters work well and use 7 parts. There
is something else called a “brick wall AM” filter that was built by a
guy in texas but i dont know much about it.


*Dr. **William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ
PJ2/K9HZ*



Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois



Owner – Operator

Villa Grand Piton - J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com <http://www.VillaGrandPiton.com>


email: @Doc_Bill <mailto:@Doc_Bill>




On Jan 3, 2018, at 10:47 AM, ohwenzelph via Groups.Io
<Ohwenzelph=yahoo.com@groups.io <mailto:Ohwenzelph=yahoo.com@groups.io>>
wrote:

“If you search the QST archives for his call”
not exactly details but helpful, with the $5 claim, I thought you
might have something specific in mind
was it the feb 1978 bc band energy-a rejection filter
or
March 1983


Alternative Filter Design
(Technical Correspondence)?
thanks

Arv Evans
 

On Wed, Jan 3, 2018 at 1:23 PM, K9HZ <bill@...> wrote:
Sorry I'm sitting in a day long meeting with only a cell phone.  The W3NQN high pass and band pass filters work well and use 7 parts.  There is something else called a “brick wall AM” filter that was built by a guy in texas but i dont know much about it. 


Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton - J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com


email:  bill@...

 


On Jan 3, 2018, at 10:47 AM, ohwenzelph via Groups.Io <Ohwenzelph=yahoo.com@groups.io> wrote:

If you search the QST archives for his call”
not exactly details but helpful, with the $5 claim, I thought you might have something specific in mind
was it the feb 1978 bc band energy-a rejection filter
or
March 1983 

Alternative Filter Design
(Technical Correspondence)?
thanks



Jacob Farnes
 

https://soldersmoke.blogspot.com/2016/01/high-pass-filter-knocks-down-am.html

Bill N2CQR made a good one that whooped the 20kW station 2 miles from me. I finally got the silver mica capacitors to finish mine. I originally built it for my RTL-SDR using ceramic caps.

560pF for the ends and 440pF (2x 220pF) for the pairs in the middle.

6uH or 35 turns on a T50-2
5.8uH or 34 on the center one to reduce ripple.

I can't use Elsie software here at work, but if you can sacrifice 160m reduce capacitance a bit, you might be able to increase rejection by moving the filter frequency higher.