|
Re: Dunstar Filters
The values can be scaled by the ratio of the frequencies. ie: 21/28 for the multiplier for the inductors and capacitors to scale to 10 meters. if you want to see the response of various filters, use a program like Elsie. Take a look at the filters used by Rick and Joanna which are the one used by PAARA at Field Day and Pacificon. Dave W6VYC
On Monday, October 7, 2024 at 11:43:22 AM PDT, Hiroki Kato <hiroki@...> wrote:
Dave, Do you have any data in re how sharp/effective this filter is? I'd like to try building one (or more for other bands besides 21MHz). Hiroki AH6CY
|
|
Re: Interstation interference book
Clif, Morgan filters look like the filters I would also recommend. Thanks for pointing them out.... Dave W6VYC
On Saturday, October 5, 2024 at 05:06:39 PM PDT, Cliff Sojourner K6CLS via groups.io <cls@...> wrote:
my FTdx10 was getting massive front end overload from KNEW, KRE, etc., on the ROV long wire antenna. recently I bought a Morgan AM BCB filter.? it is very high quality construction, very sharp skirts, deep
nulls.? really does the job!!!? handles 100w, passive, so doesn't
need a relay, getting connected to the radio TX line, etc. They offer band pass filters for all HF ham bands, too. Cliff-bob sez 2 thumbs up
On 10/5/24 16:58, David W Crocker via
groups.io wrote:
Doug,
Good bandpass filters use air
core inductors in a coupled resonator configuration which
gives lower losses and better skirts. You used to be able to
get these filters for around $100 for each band but don't know
who makes them these days. The reason I did not recommend that
Joy buy the $50 filter was the price. Also, you need to put
filters on the offending transmitters as most of the
interference comes for phase noise which is broadband and
shows up in band. The filters have to be installed with 50
ohms on both sides, so if your antenna isn't 50 ohms you need
to use a tuner between the filter and the antenna.
One of the best tricks is to
get everybody to use Magloops which are really nice bandpass
filters and an antenna.
Joy,? If you want to
experiment with these filters buy them from Doug.
Read the book that I found if
you want to see what the pros think.
Dave W6VYC
On Thursday, October 3, 2024 at 06:19:44 PM PDT, Doug
Hendricks <ki6ds1@...> wrote:
Dave,? I am curious as to why you don't think a
band pass filter can be home brewed.? I have seen
several examples on you tube that seem to work fine.?
And, back in the 90's, I used to go to the Zuni Loop
for field day.? Cam Hartford had homebrew band pass
filters for 80, 40, 20, 15 and 10.? We never had a
problem with interference and they worked great.
?
Having said that I would not advise Joy to build
one of the filters she mentioned either,? but the
reason is that it's way over priced.? I would suggest
that she order one from Qrp Labs.? It's only $4.90,
NOT $40!!!? It can easily be mounted in an Altoids
tin.
|
|
Re: Interstation interference book
¿ªÔÆÌåÓýby the way, good catch on this book.? I'm really enjoying reading
it. lotsa good stuff in there.? Cliff K6CLS CM87 On 10/2/24 11:33, David W Crocker via
groups.io wrote:
|
|
Re: Interstation interference book
¿ªÔÆÌåÓýmy FTdx10 was getting massive front end overload from KNEW, KRE, etc., on the ROV long wire antenna. recently I bought a Morgan AM BCB filter.? it is very high quality construction, very sharp skirts, deep
nulls.? really does the job!!!? handles 100w, passive, so doesn't
need a relay, getting connected to the radio TX line, etc. They offer band pass filters for all HF ham bands, too. Cliff-bob sez 2 thumbs up
On 10/5/24 16:58, David W Crocker via
groups.io wrote:
|
|
Re: Interstation interference book
Doug, Good bandpass filters use air core inductors in a coupled resonator configuration which gives lower losses and better skirts. You used to be able to get these filters for around $100 for each band but don't know who makes them these days. The reason I did not recommend that Joy buy the $50 filter was the price. Also, you need to put filters on the offending transmitters as most of the interference comes for phase noise which is broadband and shows up in band. The filters have to be installed with 50 ohms on both sides, so if your antenna isn't 50 ohms you need to use a tuner between the filter and the antenna. One of the best tricks is to get everybody to use Magloops which are really nice bandpass filters and an antenna. Joy,? If you want to experiment with these filters buy them from Doug. Read the book that I found if you want to see what the pros think. Dave W6VYC
On Thursday, October 3, 2024 at 06:19:44 PM PDT, Doug Hendricks <ki6ds1@...> wrote:
Dave,? I am curious as to why you don't think a band pass filter can be home brewed.? I have seen several examples on you tube that seem to work fine.? And, back in the 90's, I used to go to the Zuni Loop for field day.? Cam Hartford had homebrew band pass filters for 80, 40, 20, 15 and 10.? We never had a problem with interference and they worked great.
?
Having said that I would not advise Joy to build one of the filters she mentioned either,? but the reason is that it's way over priced.? I would suggest that she order one from Qrp Labs.? It's only $4.90, NOT $40!!!? It can easily be mounted in an Altoids tin.
|
|
Interstation interference book
Joy was asking about how to use a bandpass filter to limit interference at the Baylands. I don't recommend that you buy the filter. It is difficult to build analog filters good enough to limit interference. There are some good commercial filters that have been used during field events (InRad triplexer). Check out the filters that are used at Pacificon. I found this interesting book that might help. see attached. Dave W6VYC |
|
Re: Friday
I also plan to be at the Baylands for lunch and ops. I am staying for the PAARA meeting (USS Hornet Radio Station) and dinner at the Green Elephant. ? Dave W6VYC
On Wednesday, October 2, 2024 at 07:26:02 AM PDT, Hiroki Kato <hiroki@...> wrote:
I will be at the Baylands starting with lunch. Hope to see many of you. Hiroki AH6CY |
David W Crocker
.jpg)
.jpg)
David
Cliff Sojourner K6CLS
