Return Loss Bridge

Once the hole was dug for the tower I turned my attention to the antenna.  There was a little more work left to be done than I though, but we got it done.  Drill out the broken screws for the matching box cover, clean and assemble the radials and tighten lose joints etc.

I wanted to put the sna on it even though its still on the ground.  I know leaning up against a tree will have a detrimental effect, but still it should give some indication.  Once I had everything all set up I realized that I had to build a bridge.

So the the projects so far that were built due to an interest in crystal matching and crystal filters is as follows:

1, SNA
2, 20dbm attenuator
3, crystal matching jig
4, crystal filter jig
5, Return loss bridge

Not bad. 5 additional projects developed all due to the Let's build something project.

The board turned out much better than the last one so I'm encouraged.  Still some pitting, but nowhere near the same amount as last time.

73, Peter

Time for the Tower

Getting a head start on antenna season this year.  Although when I started to dig the hole this morning I was beginning to think I was right into antenna season. Warmed up soon enough, likely due to the physical work I was doing and not the wx.  At least the rain held off.

Hole is pretty much done.  Just a little touch up here and there to help with the lining up the tower.  Next sections go up Friday, hopefully, so I need to get going and finish overhauling the R5. I completed the matching box repairs. The coax connector need replacing and and a couple of solder joints were redone and evicted some spiders as well.

I'll put it together later today and sweep it with the sna. Should prove interesting seeing the results of that test.  For the good I hope.

Once this gets done I can turn my attention to my Windom.  Not so sure that layout will be optimal, but its a start.  The easiest layout will be sort of a horizontal V with the direction aiming somewhat west. Maybe even a little NW. Who knows, a little directivity may assist in my quest to have some HF contacts with members of the Peel Amateur Radio Club. 

73, Peter

Learning how to etch pcb's......again.

Just when you think you have a handle on a process, it comes up to bite you.  It took 4 attempts at toner transfer 2 tries at etching.

Problem 1 was just simple proof reading the layout before etching so that was easily cured, maybe.

Problem 2 was simply(?) controlling the heating process. Between possibly too much heat and or pressure I was getting the toner smearing/smugging slightly. This might be ok with some of the text areas, but not so much on the traces. They started to get pretty close.

What I did on my last board was put the iron directly on the toner transfer paper instead of inserting a sheet of paper in-between as I had done previously.  I found I was able to react quicker to the temperature of the board and also keep the iron much closer to the temperature needed. With the extra paper I found I needed to increase the overall temp of the iron on order to get the temp required to the board and it was quite easy to over temp.  I'm back to the porous board problem again but the board is usable. Can't fix everything in one go can one?

The discolouration is due to the sharpie I used to fil in some of the voids in the toner.  Even though I cleaned the board thoroughly, so I thought, it still has an effect.  Needs more than just scotch brite and water I suppose.

73, Peter

Crystal Matching Jig

Finished the crystal matching jig today.  I placed the bnc connectors (hopefully) to line up with the sna.  Just need to wait for the adapters to arrive to make sure they line up.  The Altoids tin is flexible enough that if I'm off a tad it should match up ok.  If not then the cables will do.

Ordered today the bnc adapters and also rubber pads for feet on my projects.  Wish I could figure out everything I need at once.  Instead I seem to be ordering something every week. Mind you its like a birthday almost every week in the mailbox. hihi. 

Yesterday  some connectors arrived along with QEX and the day before QST.  Not a bad week at all.

 

 I hope to etch my new board for testing crystal filters soon.  I may have overly complicated it a little by making provisions for something more than a 4 pole filter.  But at least the layout is done. I'll think about making it just for 4 poles or not a little more before printing. I'm using a 20 pin IC socket to place 4 crystals spaced nicely and also 2 more for holding the toroid transformers. Sil sockets will be used for the capacitors.  

73, Peter

Crystal Filter Analysis

Messed around a lot today with crystal filters and the sna.  Now that I can measure it, I have more questions that I did before.  That's way its suppose to go I guess.

Here is the data from a batch of 4 crystals previously match by another method.

ID -       crystal identification

-3dbm - bandwidth at -3dbm

Fs -      serial resonance freq.

Rs -      series resistance

Cm -     motional capacitance

Lm -     motional inductance

Q -       Quality factor

 ID      Fs   hz     -3dbm BW hz    Rs        Cm        Lm            Q
x2     4,913,469          102           8.76    0.0199    52.68     185,601
x4     4,913,475          108           9.99    0.0203    51.56     159,350
x1     4,913,487          105           9.43    0.0201    52.19     170,851
x3     4,913,487          120          14.17   0.0202    51.95     113,192

Found the match for Fs pretty good.  Although the numbers for x3 appear to be bit of an outlier and I wonder if this explains why there is a bit to much of a ripple in the pass band.  My previous post shows about a 5dbm ripple and I believe this should be around 1dbm max.  I only have 4 of the crystals on hand so I can't easily test this theory without more crystals on hand.  So instead I grabbed a bunch of different crystals and matched those.

I used a breadboard to mount the crystals and built a filter with the best ones and made some measurements. After which I put in a couple of the outliers and did see a substantial increase in the ripple. I tried changing capacitor values as well, but in the end I gave up as the breadboard is not really a good test bed for this experiment, at least as far as making definitive judgement on the values of components.  It did serve to prove however, as to what effect changes in capacitors and crystals can have on the characteristics of the filter.  I will need to design a board to facilitate in making component changes easily and quickly and allow me to have confidence in measurements.

Its amazing the amount of reading there is on this subject for such a small circuit.

73, Peter

Crystal Filter

Worked on the crystal filter today and  put the sna to the test.  Needed to play around with the settings for frequency span and frequency steps more than I though I would have to.  I didn't really think about how sharp the filter was and in order to really see the passband, the frequency span and step is very critical. I also noted, and it now makes sense, that the broader the parameters the less accurate the details are.  For example, the bandwidth and freq. max min at the -3dbm points.

Also setting the xtall input resistance does not change the characteristics of the waveform or the -3db points or bw.  It does however an effect on the data for Q, R, C, and L.

This is my first go at using the sna for the crystal filter function and I pretty sure I have set everything correctly.  There is one other parameter that I need to dig into further, but I'm sure its only needed when matching crystals.

So here's what I found out for the xtal filter for the LBS project.

These are the parameters that were set in the sna and shown in the pictures: Lo Freq. 4,913 and the Hi at 4,916. Step freq at 4hz.  I did at first span the hf band and then focused in on the crystal frequency.

1st picture shows the response when the probes were connected to the input side of the coupling transformers. The crystal input resistance was set at 50 ohms.  You can easily see the response data from the screen. 

2nd picture shows the response when the probes were connected to the input and output caps leading directly to the xtal filter and bypassing the coupling transformers. The crystal input resistance was set at 200 ohms.  Again the data is clear in the picture.  Note the bandwidth differences and the increase in the ripple. Quite a difference when bypassing the matching transformers.  It looks like in picture 1, that the ripple comes in at around 5-7dbm.  I'll need to do some reading to see how that matches up.

This is board is almost completed.  Still need to add power points and a capacitor between the amplifier circuit and coupling transformer.

So we are getting closer now to putting some of these boards together. Look for a suitable plank of wood to start with.  Its a little cumbersome with loose boards everywhere.  Likely something that will facilitate the "I let the smoke out" again. hihi.

73, Peter

XTALL Checker Jig.

Worked on my crystal checker today.  Etched the board and populated all the parts except for the BNC connectors.  I have 20 on order but they have yet to show. First time I've had to wait this long for parts.  Oh well, always a first.  In fact I've ordered so much stuff I'm losing track. Need to mark this all down on a calendar or something. I'm sure earlier I had received some diodes, but I can't find them now. Not even sure why I ordered them in the first place.

Thought I had produced my best board yet...Until I realized that I didn't do the ground pads properly.  Nothing that a jumper or solder bridge can't fix but at least the board turned out well from the toner transfer perspective.  Still some spots where the toner either didn't transfer or came off during the remove the paper stage, but good improvement from previous boards.  I used the yellow(cheap) paper I'd ordered a while back this time round as I want to make sure on the smaller boards that this paper will work and if so, I don't need to order the expensive blue stuff.

I put the board into an Altoids tin as per the rule if it fits in one, then in it goes. I put the socket for the crystal on the top of the lid and bent over the centre pin and soldered to the lid for stability.  Finished off by applying hot melt around the socket on the top side. Tight clearances for the 2 outside pins to the lid but it should be ok. Just need to drill 2 holes in the side for the BNC connectors and of course, wait for the postman.

Next up will be finishing off the crystal IF filter board.  It's mostly complete and I now have the crystals  on hand.

Worked a little on my cw at 10 wpm this afternoon.  Went well with only 3 errors.  So its coming along.

73, Peter

SNA Almost Completed

Figured out a couple of setting parameters so we are making progress and getting more comfortable in using the sna.

Did some adjustments to the LBS BPF40 and posted the results in 2 pictures below.  One shows the response from 6mhz to 8mhz.  The other is a span from 1mhz to 30mhz.  Picture of that one is not the best but it will do.

The accuracy is much better once you set the parameters closer to the operating range, but the 1- 30 gives you a look at the entire spectrum to ensure its behavior.

Not ready just yet to go over crystal matching, but hopefully soon.  Couple of parts for the crystal matching jig are a couple of weeks away.  Working on the board layout for it and should etch it in the next day or 2.

73, Peter

SNA Project

Finished putting the SNA together.  I ended up changing out 2 resistors and a cap that was suggested and parts were sent for their replacement, but I forgot to put them in. When I was having a little trouble with the setup and calibration routines, I remembered. Imagine that!!  Those routines went much smoother  and everything so far seems ok.  I'm not 100% sure that I am finished with the adjustments with the reference clock, but I'm getting there.

Built a 20db attenuator for one of the setup routines. One nice thing about have a good supply of components on hand is you can get close to the theoretical values and make up for the tolerances.  I was able to get just about bang on for the attenuator. Next up to build will be a crystal test jig. I'm now out of bnc connectors, but hopefully the ones I have on order arrive this week. They are due any day.

Maybe tomorrow Ill have a go at testing filters.  That should prove interesting.

73, Peter

SNA Project

Finally put the SNA together and the build was not to bad. My first go with the smd 805 size though. That proved quite interesting and after the first cap went on with no issue, I spent the next 10 minutes looking for the second one. Crawled all around on the floor and ended up finding it on the bench. In all I flicked about five parts. What I did notice however, they did not fly as far as the 1206's. I consider myself lucky as I found them all and if I did lose one, then I may have been stuck as my on-hand inventory is 1206 size.

I took a little more care with the 805's, using tweezers that I could control the pressure and not the self clamping ones I use with the 1206. As well I did not fiddle around to much once the part was one the board. I figure if I got it there, then don't press my luck. 

I'm part way through the setups, and so far so good. The regulators run a little hot, and I'm a little concerned once it is all in a case. Worry about it more later.

There is a lot in this instrument and I suspect a fair bit of reading.  I'll have to break down and print it all off I suppose.  Easier to read it outside with a beer before the weather turns.

First picture is a shot of the opening splash.  The 2nd shows the underside with the DDS 60 board installed and the 3rd, top side with the touchscreen removed.

73 for now, Peter

Change of Pace

Something a little different today.  No building and operated instead. First contact on my new KX3 to Maryland was pretty nice. Tried to work a friend in Toronto on a few of the bands and no luck there.  We tried ssb but at the end I listened for a cw beacon which I think I heard way down in the mud.  Looks like CW will be the way to go for contacts back to the old QTH area.  Set up my 40 meter dipole and qrp station in the back yard and had a great afternoon.

Back to building next week.

73, Peter
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