EMRFD Message Archive 1293
Message Date From Subject 1293 2008-01-03 10:22:15 Nick Kennedy Hycas IF amp & crystal frequencies
really nicely done -- almost erases my guilt over using a board at
all. ;^)
One of my next steps will be to build some crystal filters and a BFO,
so I need to decide on a frequency and order some crystals. I guess
avoiding harmonics in the ham bands and frequencies with strong
stations on them are two main considerations, right(?)
Looking at Mouser & DigiKey a little, I don't see a lot of choices in
9 MHz crystals. More around 9.216 and 8.192. I might also consider
4.9152. Any comments on drawbacks associated with those choices?
Am I correct in assuming that the "full sized" HC-49/U crystal is
likely to have better Q than the shorter ones such as HC-49/US and the
SMT versions? My limited measurements would indicate that that's the
case.
Some of the spec sheets I pulled up have some alarming typical Rs
specifications of around 35 to 60 ohms and higher. Does that seem
high? Maybe those are "worst case" values. I guess Q could still be
good if Lm were high and Cm low, but I'm not counting on that.
Crystals I've measured in the 4.9 to 9 MHz range have had Rs values of
5 to 15 ohms. I hope my measuring technique was accurate.
Comments on choices of IF frequency, availability of crystals, ones to
avoid and ones proven OK? It's understood I'm looking for "stock"
crystals to keep my costs down.
73--Nick, WA5BDU1294 2008-01-03 12:45:39 Robert Cerreto Re: Hycas IF amp & crystal frequencies
I have been doing the same thing for several weeks.
As far as what frequency to use, it kinda depends what bands you are talking about. There is no magic frequency that fits all situations. The topology of your receive chain also has a bearing on IF frequency selection i.e. up converstion, down converstion etc. W7ZOI has a handy utility program called SPURTUNE. Plug in you IF freq. and BFO/LO freqs and it will show you where the spurs are. However, it will not tell you magnitudes. There are other programs on the 'net that will do that to.
In general, the HC49 format is higher Q. ECS and FOX crystals (both less than 0.50 each) both seem to have consistant and Q's from 140000 and higher, Rs 5 to 7 ohms. If you are building a 5 pole filter, order about twenty of them. Then use the EMRFD methods to characterize them. Then use the EMRFD software to design your filters. It helps to read all of W7ZOI's previous papers on crystal filter design too.
If you build a jig for the characterization, don't forget to keep all your leads short. I don't have one reccommendation for the jig unless I know what kind of test gear you have. You must drive the crystal from a solid 50 ohm source with a 1Hz resolution. The detector can be an SA, power meter that is also a solid 50 ohm input. Don't drive the crystal too hard. I use about -30Dbm. Pad the generator to absolutely guarentee 50ohms.
Hope that helps a bit.
72, Bob WA!FXT
Nick Kennedy <kennnick@gmail.com> wrote:
I'm about 2/3rds done building my IF amp & AGC board. The board is
really nicely done -- almost erases my guilt over using a board at
all. ;^)
One of my next steps will be to build some crystal filters and a BFO,
so I need to decide on a frequency and order some crystals. I guess
avoiding harmonics in the ham bands and frequencies with strong
stations on them are two main considerations, right(?)
Looking at Mouser & DigiKey a little, I don't see a lot of choices in
9 MHz crystals. More around 9.216 and 8.192. I might also consider
4.9152. Any comments on drawbacks associated with those choices?
Am I correct in assuming that the "full sized" HC-49/U crystal is
likely to have better Q than the shorter ones such as HC-49/US and the
SMT versions? My limited measurements would indicate that that's the
case.
Some of the spec sheets I pulled up have some alarming typical Rs
specifications of around 35 to 60 ohms and higher. Does that seem
high? Maybe those are "worst case" values. I guess Q could still be
good if Lm were high and Cm low, but I'm not counting on that.
Crystals I've measured in the 4.9 to 9 MHz range have had Rs values of
5 to 15 ohms. I hope my measuring technique was accurate.
Comments on choices of IF frequency, availability of crystals, ones to
avoid and ones proven OK? It's understood I'm looking for "stock"
crystals to keep my costs down.
73--Nick, WA5BDU
---------------------------------
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[Non-text portions of this message have been removed]1295 2008-01-03 16:57:33 Allison Parent Re: Hycas IF amp & crystal frequencies 1296 2008-01-03 17:17:05 Jim Kortge Re: Hycas IF amp & crystal frequencies
>I guess I haven't worried about "ham band" harmonics as much as high powered
> One of my next steps will be to build some crystal filters and a BFO,
> so I need to decide on a frequency and order some crystals. I guess
> avoiding harmonics in the ham bands and frequencies with strong
> stations on them are two main considerations, right(?)
stations outside of the bands. I try to design the output filters to take care
of the harmonic energy. Some of those shortwave broadcast stations run whopping
amounts of power, so those worry me more.
>I generally try to stay away from even frequency crystals like 5,6,8, etc. MHz
> Looking at Mouser & DigiKey a little, I don't see a lot of choices in
> 9 MHz crystals. More around 9.216 and 8.192. I might also consider
> 4.9152. Any comments on drawbacks associated with those choices?
assuming that something with RF high output will be on one of those frequencies,
including WWV etc. That said, if 9 MHz were easy to come by I'd still use that
frequency because of the latitude in designing for two bands more easily. I use
Wes' Spur Tune program to determine where the spurs will be. Very handy. Some of
the higher order spurs might have to be tolerated though.
>Mine too. And quite significant differences in Q from the large case crystals to
> Am I correct in assuming that the "full sized" HC-49/U crystal is
> likely to have better Q than the shorter ones such as HC-49/US and the
> SMT versions? My limited measurements would indicate that that's the
> case.
the smaller ones, with the HC49/U units being consistently much better.
>I think the manufacturers are covering their back sides using those high Rs
> Some of the spec sheets I pulled up have some alarming typical Rs
> specifications of around 35 to 60 ohms and higher. Does that seem
> high? Maybe those are "worst case" values.
values shown in the spec sheets. That makes sure you can't send back a set of
crystals that are really low Q and unsuitable for filter use.
I guess Q could still be
> good if Lm were high and Cm low, but I'm not counting on that.They probably are. I generally see Rs values from 5 to maybe 25 Ohms depending
> Crystals I've measured in the 4.9 to 9 MHz range have had Rs values of
> 5 to 15 ohms. I hope my measuring technique was accurate.
on the supplier. ECS and Fox seem to be the overall best from my experience.
Vishay-Dale used to be good, but aren't anymore. In general, the move to
manufacturing in China is producing crystals with higher Rs values and a lot
more variabililty in the more recent samples I've tested. :-( I don't think the
higher and more variable Rs values is an issue for most applications, but sure
affects the insertion loss of the filters we make.
One of my test setups uses has the crystal being driven via step down
transformers at either end of the crystal and the other is all resistive. Both
seem to produce the same kind of results. I won't say identical, because they
aren't. But then, there is enough variability in measuring crystals that
measuring the same set repeatedly produces slightly different results with
either of my setups.
>I have used 4.9152, 7.3728 and 11 MHz very successfully in several rigs, and
> Comments on choices of IF frequency, availability of crystals, ones to
> avoid and ones proven OK?
4.4336 for one rig. No major problems with any of those frequencies.
It's understood I'm looking for "stock"
> crystals to keep my costs down.Yes, custom crystals will at least double the price of stock units and you have
to order 2000 or so to get a decent price break with 8-10 weeks for delivery.
Don't ask my how I know! :-)
72 and GL Nick; Keep on pickin'!
Jim, K8IQY1297 2008-01-03 17:56:19 aa7ih_ray Re: Hycas IF amp & crystal frequencies
I too am in the middle of building what I hope will be a high
performance receiver. Initially it will be constrained to 40 m CW,
i.e., 7.000 to 7.100 MHz. The preselector/LNA is done. The mixer
will be determined by the outcome of a series of experiments with H-
Mode, cascade and diode-ring (currently diode-ring). Presently I am
in the process of constructing a crystal filter. The first of which
will be a 4-pole 9 MHz with a design bandpass of about 400 Hz.
The local oscillator for such a scheme will be setup for low-side
injection, 1.900 to 2.000 MHz, squarely in the upper half of 160
meters. The second harmonic will fall in the range 3.800 to 4.000
MHz; the upper end of 80 meters. The third harmonic, usually the
strongest, falls outside any Ham band.
I purchased forty 9-MHz crystals in an HC-49/US case from Jameco. I
have been underwhelmed by the poor ESR and Qs that I've measured:
ESRs in the 28 to 40 Ohm range and Qs ranging from 54,000 to 76,000.
Lm and Cm were measured with the G3URR circuit (EMRFD, page 3.19).
Rm was measured with an AC bridge driven by a homebrew VXO. My
trusty HP8640B proved too unstable and drifty for crystal
characterization service.
I've decided to go ahead and build the filter anyway although I am
not expecting stellar performance and I cannot recommend it. This
should be a good learning experience and for me, that's what building
is all about.
When selecting an IF look at Local Oscillator frequencies and
harmonics. Decide on high-side or low-side injection and look at
where the image frequencies will fall. The downside of not using a 9-
MHz IF is that the Hycas IF Amp will need to be retuned for your new
frequency. Probably not a problem.
My crystal filter will be followed by a Hycas IF Amp/AGC. The kitlet
is presently on my bench and trembling to be constructed.
Good luck.
73,
Ray, AA7IH1299 2008-01-03 22:30:58 cwfingertalker Re: Hycas IF amp & crystal frequencies
I chose to use the 9 mhz IF stream. I ordered two 9 mhz crystal kits from INRAD.
Also some BFO crystals from them too. These filters have a 200 ohm impedance so I
reworked the L network for a proper match. These kits have four crystals and include
the capacitors. One has a CW bandwidth of 600 hz and the other 2400 hz for SSB. I
plan to build them in a separate boxes. Also will include an L network so the filter
box will have a 50 ohm port for easy connection using 50 ohm coax to the IF board.
The price is reasonable. Check out the website. http://www.inrad.net/
home.php?cat=149
So far I am thinking of single banders. Maybe 40 and 80 meters CW only. I am still
up in the air about up or down converting. Same with the VFO frequency. A duo
bander is possible for 80 and 20 meters. I have to pencil it all out yet.
73
Bill N7EU1300 2008-01-04 06:36:07 Robert Cerreto Re: Hycas IF amp & crystal frequencies
Need some advice and/ r sounding board.
I completed the HYCAS on my own board several weeks ago. I am now designing the filters for it using 11 mhz ECS stuff. The initial prototype of a 7 pole (only took 11 crystals to get matches) filter is complete and working fine and I am now waiting for a bag of 100 from mouser. I was going to construct a series offilters for progresively narrower bandwidths. But, you have given me an idea. A wide filter at the goes into point of the amplifier and more, less poles narrow filters at the goes out point of the amplifier. Assuming each set of filters has the same center frequencies will this reduce wide band noise? And will this method steepen skirts more effectively than just many pole filters on the input side of the HYCAS? What is the advantage to splitting the selectivity across the HYCAS instead of lumping it before the HYCAS?
I am not a full time RF engineer so, please excuse my naive questions. I flying through this stuff on intuition and a lot of hard work experimenting.
Thanks for your past help and I amlooking forward to your next answer.....piece of education.
73, Bob WA!FXT
Allis1302 2008-01-04 14:42:11 brainerd@wildblue... Re: Hycas IF amp & crystal frequencies
> Hey Allison,I have seen designs that replace the capacitors with varicaps which allow a
>
> Need some advice and/ r sounding board.
>
> I completed the HYCAS on my own board several weeks ago. I am now designing the filters for it using 11 mhz ECS stuff. The initial prototype of a 7 pole (only took 11 crystals to get matches) filter is complete and working fine and I am now waiting for a bag of 100 from mouser. I was going to construct a series offilters for progresively narrower bandwidths. But, you have given me an idea. A wide filter at the goes into point of the amplifier and more, less poles narrow filters at the goes out point of the amplifier. Assuming each set of filters has the same center frequencies will this reduce wide band noise? And will this method steepen skirts more effectively than just many pole filters on the input side of the HYCAS? What is the advantage to splitting the selectivity across the HYCAS instead of lumping it before the HYCAS?
>
> I am not a full time RF engineer so, please excuse my naive questions. I flying through this stuff on intuition and a lot of hard work experimenting.
>
> Thanks for your past help and I amlooking forward to your next answer.....piece of education.
>
> 73, Bob WA!FXT
>
variable bandwidth filter. The disadvantage is the varicaps will limit the
strong signal capability of the filter.
Dave - WB6DHW
<http://wb6dhw.com>1303 2008-01-04 15:53:23 Allison Parent Re: Hycas IF amp & crystal frequencies 1304 2008-01-04 15:58:43 Allison Parent Re: Hycas IF amp & crystal frequencies 1305 2008-01-04 16:19:13 Nick Kennedy Re: Hycas IF amp & crystal frequencies
couple questions & providing more info-
I usually characterize crystals using a hacked together K8IQY PVXO for
a signal generator, with the crystal sitting between two 50 to 12.5
ohm resistive pads. I use Hayward & Larkin's log power meter, built
from a Kanga "kitlet", for the detector. I also sometimes use the
G3UUR circuit, but it doesn't give Rs. That's probably not a major
issue though.
Beyond the filters, there will some trail and error on other major
stages, but for now I'm planning to use an NJQRP DDS-60 board for the
LO. I like to do some programming and have already written several
DDS control programs, so that'll work out well. I've also considered
a multi-PIG PLL/VCO but like the wide range of the DDS. I think I can
get the PLL/VCO up to about 20 MHz.
At least initially, I'll use diode balanced mixers from the mixer &
product detector, probably commercial ones I have in my junk box.
On the audio end, I'm thinking of using a portion of a spare R1 board
I happen to have on hand. I shouldn't need all its gain, since it's a
self-contained DC receiver. But I like the hefty audio amplifier
using two big TO220 transistors.
Fun, fun, fun. I finished the IF board. The variable capacitor
shorted out, probably because it was cocked forward when I soldered it
in. After replacing it, I started testing and the board seems to be
working OK, within the limits of the test equipment I have. I fed the
9 MHz output of my PVXO to it through a step attenuator and watched
the AGC voltage change. The RF output was quite steady at about
-36dBm. Right now that's a little low to look at with my scope, so
I'm going by numbers only.
73--Nick, WA5BDU1306 2008-01-05 06:25:17 Allison Parent Re: Hycas IF amp & crystal frequencies 1307 2008-01-10 09:07:59 Graham Fabricate your own vacuum tubes.
For relevant content there is a ham radio transmitter built using
these home made tubes. Also seemed to build his own
high vacuum pumps, too.
http://dailymotion.alice.it/video/x3wrzo_fabrication-dune-lampe-triode
Let's see. If I was going to build a Pentium IV using triodes, at about
4 square inches
per tube for 50,000,000 transistor equivalent, it should take about
1,400,000 square
feet. I have not figured the power.
--- Graham / KE9H
==1308 2008-01-10 14:59:40 ted Re: Fabricate your own vacuum tubes.
semiconductors.
Ted
N3Ted
On Thu, 2008-01-10 at 11:07 -0600, Graham wrote:
>
> Interesting video of a Frenchman fabricating his own vacuum tubes.
> For relevant content there is a ham radio transmitter built using
> these home made tubes. Also seemed to build his own
> high vacuum pumps, too.
>
> http://dailymotion.alice.it/video/x3wrzo_fabrication-dune-lampe-triode
>
> Let's see. If I was going to build a Pentium IV using triodes, at
> about
> 4 square inches
> per tube for 50,000,000 transistor equivalent, it should take about
> 1,400,000 square
> feet. I have not figured the power.
>
> --- Graham / KE9H
>
> ==
>
>
>
>
>1309 2008-01-11 04:06:55 w4zcb77 Re: Fabricate your own vacuum tubes.
> For relevant content there is a ham radio transmitter built using
> these home made tubes. Also seemed to build his own
> high vacuum pumps, too.
the 4 newsgroups I subscribe to. I haven't looked at it, and it's
possible that the guy has something to offer, but in Clinton B. DeSotos
book, there is the discription of a young amateur doing the same thing
(Successfully) with a lot less back in the early 1930's.
W4ZCB1310 2008-01-11 04:42:51 sp9mrn Re: Fabricate your own vacuum tubes.
http://tubedevices.com/alek/pwl/lampy_produkcja/lampy_produkcja.htm
and homebrew nixie:
http://tubedevices.com/alek/pwl/lc1d/homemade_nixie_tubes.pdf
http://tubedevices.com/alek/pwl/ls1/ls1_e.htm
and others
http://tubedevices.com/alek/pwl/pwl_e.htm
73
MAc
sp9mrn1347 2008-01-19 15:18:15 jr_dakota Re: Fabricate your own vacuum tubes.