EMRFD Message Archive 1003

Message Date From Subject
1003 2007-08-31 10:49:26 Hari G Spectrum Analyzer BPF
All,

Can someone give me the digikey partnumber for the Hammond box and
the SG caps used in the BPF of the ZOi SA.

BestRegards
Hari
1006 2007-09-01 11:45:22 Wes Hayward Re: Spectrum Analyzer BPF
Hari, et al,

I assume that you are talking about the 110 MHz VHF Bandpass filter
and not one of the 10 MHz (or 10.7) filters.

The original filter was built in a Hammond 1590B, which is DigiKey
HM151-ND. The variable capacitors I used were Sprague-Goodman
GGP8r500 with a spec of 0.8 to 8.5 pF and 750 volts. The parts that
N8ET sent out from Kanga may well be something slightly different,
depending on where he could find some good prices. But he confirmed
that anything that was different still worked well.

Note that Kanga US is now shut down because of severe flood damage to
all inventory. We don't know what will evolve from this situation.
Keep an eye on the Kanga US website.

I have a new website that now includes both the up to date spectrum
analyzer page and a much older page that had some early info. The
new web page is http://w7zoi.net/

Please do not feel that the 110 MHz filter must be duplicated with
exactly the components that I used. You can do as well with a
homemade box using about any conductive material, so long as it is
well sealed. This includes boxes made from soldered scraps of metal
and/or circuit board material. Experiment and measure. One thing
that is vital: The 110 MHz bandpass filter is a rather open
structure. As such, it works fine at VHF, but suffers from poor
stopband attenuation at UHF. This is easily fixed with a low pass
filter with a cutoff of around 130 MHz. This is a place where it is
extremely easy to build such a filter with SMT components, even if
you have never done SMT in the past. And it is also a place where
SMT parts really work well and are justified. Details are
1007 2007-09-01 19:27:39 Hari G Re: Spectrum Analyzer BPF
Wes,
 
  Good to hear form you after long time.
 
I couldnt find the same part numebr in the Digikey listing there are some other parts may be i will look for the nearest one available.
 
To clarify , is it ok if i use a normal ceramic trimmer with max 10PF capacitance,  calibrate and close the box ? Iam not sure hopw easy it will be as i will be using POS200 and AD8307 to do this along with a freq counter.
 
Working with SMD is not an issue now  after building my STAR radio, where do i fix the LPF is it inside the BPF box or ouside.  
 
I looked at your site,  pdf files are very easy to store/print.
 
Best Regards
 Hari
VU2GHB

 
On 9/2/07, Wes Hayward <w7zoi@easystreet.com> wrote:

Hari, et al,

I assume that you are talking about the 110 MHz VHF Bandpass filter
and not one of the 10 MHz (or 10.7) filters.

The original filter was built in a Hammond 1590B, which is DigiKey
HM151-ND. The variable capacitors I used were Sprague-Goodman
GGP8r500 with a spec of 0.8 to 8.5 pF and 750 volts. The parts that
N8ET sent out from Kanga may well be something slightly different,
depending on where he could find some good prices. But he confirmed
that anything that was different still worked well.

Note that Kanga US is now shut down because of severe flood damage to
all inventory. We don't know what will evolve from this situation.
Keep an eye on the Kanga US website.

I have a new website that now includes both the up to date spectrum
analyzer page and a much older page that had some early info. The
new web page is http://w7zoi.net/

Please do not feel that the 110 MHz filter must be duplicated with
exactly the components that I used. You can do as well with a
homemade box using about any conductive material, so long as it is
well sealed. This includes boxes made from soldered scraps of metal
and/or circuit board material. Experiment and measure. One thing
that is vital: The 110 MHz bandpass filter is a rather open
structure. As such, it works fine at VHF, but suffers from poor
stopband attenuation at UHF. This is easily fixed with a low pass
filter with a cutoff of around 130 MHz. This is a place where it is
extremely easy to build such a filter with SMT components, even if
you have never done SMT in the past. And it is also a place where
SMT parts really work well and are justified. Details are

1010 2007-09-03 20:32:01 Wes Hayward Re: Spectrum Analyzer BPF
Hello Hari and group,

Well, I think you want some sort of a trimmer capacitor that can be
adjusted from the outside of the closed box. It will otherwise be
very difficult to adjust. The variable capacitor is essentially the
only capacitor in each resonator, which is good for experimental
ease. However, it may make it difficult to tune with a ceramic
trimmer. The Sprague capacitors I used were multiple turn things, so
they are very easy to use. That is why they are expensive.

The low pass filter should be on the outside of the box on a small
circuit board. It may not even have to be shielded if it is kept
small.

I'm sure you will have no trouble with this filter if you have built
a PICaSTAR.

Good luck.

73, Wes
w7zoi


1012 2007-09-04 09:50:02 Hari G Re: Spectrum Analyzer BPF
Wes ,
 
  Thanks , iam not able to find a source for this capacitor if you know of some in the US let me know.
 
Pic A Star  is working and that is the rig that iam using now , now i need to build the SA to check the DDS and make some measurements.I have built Star with a PC based DDS wobbler and a multimeter !
 
BestRegards
  Hari

 
On 9/4/07, Wes Hayward <wesw7zoi@gmail.com> wrote:

Hello Hari and group,

Well, I think you want some sort of a trimmer capacitor that can be
adjusted from the outside of the closed box. It will otherwise be
very difficult to adjust. The variable capacitor is essentially the
only capacitor in each resonator, which is good for experimental
ease. However, it may make it difficult to tune with a ceramic
trimmer. The Sprague capacitors I used were multiple turn things, so
they are very easy to use. That is why they are expensive.

The low pass filter should be on the outside of the box on a small
circuit board. It may not even have to be shielded if it is kept
small.

I'm sure you will have no trouble with this filter if you have built
a PICaSTAR.

Good luck.

73, Wes
w7zoi

1013 2007-09-04 23:36:38 jr_dakota Re: Spectrum Analyzer BPF
I got the KangaUS kit last year ... the caps used by Bill were JFD
model VCJ2398 0.5 - 16 pF, 500v. 0.28" diameter, 3/4" long. I don't
know if this is Bill's source but I found a picture and description at
Surplus Sales of Nebraska
http://www.surplussales.com/Variables/PistonTrimmers/PistCap-2.html
about 3/4 of the way down the page

They worked just fine, in fact that bandpass filter was my biggest
concern since I don't usually work at those frequencies and have
limited test equipment for that range .... I was pleasantly surprised
how well it turned out with a minimum amount of tweaking and although
it has slightly more loss than I think it should have, it's not that
far off (About 1-2 Db) nor does it seem to hurt the performance of the
finished unit ... One thing that did throw me was they came set at max
capacitance which is about twice the value of the ones Wes used and
several turns didn't get them where they needed to be so I ended up
pulling and measuring them
1014 2007-09-05 10:08:25 Hari G Re: Spectrum Analyzer BPF
Jr ,
 
     Thanks for the details , i just ordered those now !.
 
Could you tell me how you adjusted the BPF ? , iam looking at using the AD8307 and PIC with  DAC to roughly sweep through the voltage needed and then plot it in the PC.
 
OZ2CPU (iam not sure on the call sign) he has given a power meter which is capable of sending the reading on the serial port i think Picpower can also do that. Iam not sure if i will be able to the AD dac used. 
 
Many Thanks
 
Best Regards
    Hari
 VU2GHB
 
On 9/5/07, jr_dakota <SG2112@yahoo.com> wrote:

I got the KangaUS kit last year ... the caps used by Bill were JFD
model VCJ2398 0.5 - 16 pF, 500v. 0.28" diameter, 3/4" long. I don't
know if this is Bill's source but I found a picture and description at
Surplus Sales of Nebraska
http://www.surplussales.com/Variables/PistonTrimmers/PistCap-2.html
about 3/4 of the way down the page

They worked just fine, in fact that bandpass filter was my biggest
concern since I don't usually work at those frequencies and have
limited test equipment for that range .... I was pleasantly surprised
how well it turned out with a minimum amount of tweaking and although
it has slightly more loss than I think it should have, it's not that
far off (About 1-2 Db) nor does it seem to hurt the performance of the
finished unit ... One thing that did throw me was they came set at max
capacitance which is about twice the value of the ones Wes used and
several turns didn't get them where they needed to be so I ended up
pulling and measuring them

1017 2007-09-08 10:12:12 jr_dakota Re: Spectrum Analyzer BPF
I used the POS-200 as a signal source with a digital milliwatt meter
and a frequency counter for measurement .... If I remember right I
also used -3db 50 ohm pads on the input and output to make sure the
impedances matched and the filter was properly terminated ..... I
played with it for 2 or 3 nights to learn as much as I could and to
make sure it was right as it seems to be important to the performance
of the overall unit and because I noticed some people had trouble with
it .... Note also it's a good idea to sweep it well outside it's range
to to make sure the ultimate rejecti
1018 2007-09-08 11:46:14 Hari G Re: Spectrum Analyzer BPF
Jr ,
 
 Thanks for the details, my first baord is ready to solder , by the time i finish the baords i think the caps will come and i can build the BPF.Mine will be 110.7 as i havea 50Khz and 6Khz 10.7 filters with me.
I collected most of the parts , tomorrow i will be soldering the first mixer and the the oscillator.
 
Do you have the part number of the Fixed value caps (C601/C604/C607) used in the BPF , i wanted to buy the same as used in that if its available with digikey.
 
Best Regards
 Hari
 

 
On 9/8/07, jr_dakota <SG2112@yahoo.com> wrote:

I used the POS-200 as a signal source with a digital milliwatt meter
and a frequency counter for measurement .... If I remember right I
also used -3db 50 ohm pads on the input and output to make sure the
impedances matched and the filter was properly terminated ..... I
played with it for 2 or 3 nights to learn as much as I could and to
make sure it was right as it seems to be important to the performance
of the overall unit and because I noticed some people had trouble with
it .... Note also it's a good idea to sweep it well outside it's range
to to make sure the ultimate rejecti

1019 2007-09-08 20:09:17 Wes Hayward Re: Spectrum Analyzer BPF
Hi Hari, and group,

Boy I'm sorry, but I have no idea what the capacitors were that were
kitted by Bill, N8ET, at Kanga. He would probably not know either,
for he lost almost all of his parts and probably the records that go
with them in a recent flood. This was more than a casual leak that
you can fix by calling a plumber, or your buddy next door. (I had
one of those the other day and it was frustrating enough -- I hate
plumbing! But it was nothing compared with Bill's problems.) This
was the kind of flood that filled his basement with water and caused
a piano to drift all over the place. It finally stabilized when the
water pressure caused a sliding glass door to break out.

But for the capacitors, it does not matter a lot. I would buy some
reasonable capacitors, but I don't know what the caps were in the
units I built. I got my capacitors from the Tektronix Company Store
when some of their management decided to save money by getting rid of
engineering stock. So it was all declared surplus. When I bought
the caps from the company store, I split them with a friend and then
sorted them by value. I don't even have the Tektronix part numbers
for most of them. I'll take a look in my stuff, but I doubt that I
have any viable data other than C and TC. At the time, I was
especially interested in NP0 caps for use in VFOs. If I come up
with anything, I'll put it on the group page.

If I were building the project, I would probably open the Digi Key
catalog, go to the Panasonic page, and order some 15 pF and 18 pF COG
caps. I'd probably go for 5%, for that is close enough. And 50
volt breakdown is fine. I said Panasonic, but I'm sure that some
other brands are just as good.

Sorry that I can't give you better information. Get something and
try it. If the insertion loss is high, try something different.

Good luck.

73, Wes


1020 2007-09-09 10:22:42 Hari G Re: Spectrum Analyzer BPF
Wes ,
 
  I read about the floods and also Kanga will be down for some time from their website.Hope he will be back in action soon.
I was curious looking at one of the pictures of the BPF in your site with and yellow coloured cap with axial leads.Anyways i will try as suggested for panasonic or any other which is COG/NPO with leads. 
Thanks for the help , i have tinned the boards today and they are now ready to be assembled. 
 
I did one modification to the final detetctor alone by replacing that with an AD8307,  rest of the IF protions remains intact.Hope this does not create much of a trouble.
 
Best Regards
   Hari  
 
On 9/9/07, Wes Hayward <wesw7zoi@gmail.com> wrote:

Hi Hari, and group,

Boy I'm sorry, but I have no idea what the capacitors were that were
kitted by Bill, N8ET, at Kanga. He would probably not know either,
for he lost almost all of his parts and probably the records that go
with them in a recent flood. This was more than a casual leak that
you can fix by calling a plumber, or your buddy next door. (I had
one of those the other day and it was frustrating enough -- I hate
plumbing! But it was nothing compared with Bill's problems.) This
was the kind of flood that filled his basement with water and caused
a piano to drift all over the place. It finally stabilized when the
water pressure caused a sliding glass door to break out.

But for the capacitors, it does not matter a lot. I would buy some
reasonable capacitors, but I don't know what the caps were in the
units I built. I got my capacitors from the Tektronix Company Store
when some of their management decided to save money by getting rid of
engineering stock. So it was all declared surplus. When I bought
the caps from the company store, I split them with a friend and then
sorted them by value. I don't even have the Tektronix part numbers
for most of them. I'll take a look in my stuff, but I doubt that I
have any viable data other than C and TC. At the time, I was
especially interested in NP0 caps for use in VFOs. If I come up
with anything, I'll put it on the group page.

If I were building the project, I would probably open the Digi Key
catalog, go to the Panasonic page, and order some 15 pF and 18 pF COG
caps. I'd probably go for 5%, for that is close enough. And 50
volt breakdown is fine. I said Panasonic, but I'm sure that some
other brands are just as good.

Sorry that I can't give you better information. Get something and
try it. If the insertion loss is high, try something different.

Good luck.

73, Wes

1021 2007-09-09 10:36:15 Wes Hayward Re: Spectrum Analyzer BPF
Hi Hari, group,

No, a change to an AD8307 should present no problems at all. Most
of us are now using that part in our analyzers. In fact, I think
that was the only log board that Bill had in the kit. Also, I think
I even put that change in Ch 7 of EMRFD.

Time now to build the thing and start throwing some signals at it.

Good luck.

73, Wes


1022 2007-09-10 18:55:18 Hari G Re: Spectrum Analyzer BPF
Wes ,
 
  Looks like the panasonic part is not not stocked by Digikey but they have Murata caps.
 
I have started the work , the lat part to go in will be the 110.7Mhz BPF .Let me first see something !
 
Many Thanks 
  Hari