Jerry,
I have been following all of the threads you have listed above.? Note that the low pass filter by Ashhar is the newest.? I have read that Raj has agreed that either the LCL filter OR his replacement of L5 and L7 do reduce the spurs.? The solution from Ashhar is more complex, in that there are bias resistors that need to be replaced as well.

Ashhar stated in the 61645 thread that the "relays as supplied now" do not need to be replaced.? It is not clear if that means that there are new parts being installed in the current shipping product, or if the originals are OK from v4 boards.? I have been looking for someone to receive a v5 board in the hopes that all of the corrections needed are on that board and we can lay to rest the correct solution to use to solve the spurs and harmonics.

In the meantime I am off the air until I do something.? That may be wait for the QSX from QRPGuys if it becomes available before a v5 board from HF Signals.

73
Evan
AC9TU

Yes, they (C215 and C211) are still installed, however look close at C211 in the picture? The left side of the cap was connected to L7.? It is now not connected to anything.? That is not the case for C215, it is still in series with the filter.

The question was not if it worked or not, I am taking the feedback from ubitx.net that it does.? My prior email was more a question for my understanding rather than clarification on how to do it.

73
Evan
AC9TU

Note that Raj, who came up with this fix, has reported that these should be shielded surface mount parts.
? ??/g/BITX20/message/60946
The thread is worth reading.

Ashhar recommends a T low pass filter of 0.3uH-47pF-0.3uH to knock out the 90mhz 2'd harmonic
of the 45mhz IF amp before it hits the mixer at D1,D2:
? ??/g/BITX20/message/61645
This kills the spur going out over the air at 2*45mhz-(45mhz+DialFreq) = 45mhz-DialFreq,
only needed for 15m, 12m and 10m SSB transmissions.
He uses a T30-6 torroids to create those 0.3uH inductors, might be better off with Raj's shielded surface mount inductors?

And also recommends a 12mhz trap, I assume we have a 12mhz spur going out over the air otherwise:
? ??/g/BITX20/topic/28049653
Since clk2 is always above 45mhz, perhaps a 30mhz high pass filter would be easier to reproduce here.

Jerry

I inspected T1 and T2 nothing obvious.? I checked continuity for the connected wires on t1 and t2 seems ok.? Yes I did get a loud tone with those injected values at TP16 and TP17.

I don't have any amp components.? I have one on order not due till early Jan.? Where were you thinking to connect the audio amp?

I don't have enough experience to suggest the below possibilities but sort of a gut feel:
It sounds like I get enough static volume on my earpiece? and with 1khz tones with the right power and frequency it can get ear splitting loud on earpiece.? ?The underlying signal itself sounds low relative to the noise I think.
Sounds like the detected signal isn't amplified enough, I get plenty of noise amplification though :)??

Evan, thanks for the reply. Haven’t received the smd inductors yet so still have time to figure it out ??

73,
Guy WB7SZI?

If you're in the "$1K+" price range, the Rigol TS850TG (and that TG is VERY important if you're serious) is my choice bar none for the serious RF experimenter. A close second would be the Siglent equivalent. The resolution bandwidth goes down to 10 Hz, and that "TG" or tracking generator is vitally important for two-port testing, like sweeping the response of filters and antennas. I've had mine for a little over a year now and I couldn't be happier! It is a real SA with all the bells and whistles any advanced experimenter would need. Any needs this one wouldn't cover and you're now in the $5K on up range, like an entry level HP or whatever. I come from a 20 year career in RF design engineering and I've used analyzers in the $50-$100K range. You could say I was very spoiled during that career. However, my hobbies are not going to take over my now limited budget and I very carefully choose what tools I purchase. You won't be sorry with a Rigol, I'm sure. The TG is integral with the instrument so you MUST order it that way; it cannot be added after the fact as a modification. The Siglent equivalent has the TG hardware in the base unit, but to enable the TG you need to buy that software separately. In the end they are very competitive and are around the same price.
I hope this helps,
Larry

开云体育

I am guessing here, but it seems like the signal generator is being loaded down by T2.? That might explain why you are getting better results when further up the LPF.? If there is a problem, then I would look at T2.? Inspect it closely for any leads being shorted (i have read that was a problem for another person's board).

Beyond inspection, I would not have another way to test that part.? Maybe someone else has an idea or suggestion on how to test.?

To support the above, when you inject the 12mhz signal at T16/17 are you getting a very load tone out of the audio speaker/headphone?? I am not sure what the .1PP measurement should be, and my board is down for spurs and harmonics correction surgery, so I cannot test it.? Trying to isolate in my mind if the problem is in the RF or AF sections of the receiver.? My current hunch is more on the AF side,? If you have an audio amp that can work at microphone input levels (computer amplified speakers would not have the input sensitivity) then you could try that.? You could build an audio preamp with an op amp ic, assuming you have the parts for that kind of construction.? One based on a 741 op amp has been listed in one of the threads on BITX20.

73
Evan
AC9TU

I redid some tests

7.150MHZ
TP2 - 100uv gave 88mv p-p, 200uv gave 144 p-p - estimated those may be a little high given my frequency generator only put out 2.4v when set at 3.5v and can't measure just calculating uv.

TP1 - 900uv gave .1 p-p

TP13 I tried 3rd harmonic at 17.383 since my generator only goes to 25MHZ I couldn't get a tone. but if putting in estimated 2900uv got .1p-p

From my previous tests:
TP17 at 11.99 or so I could get a tone 480mv gave .1v p-p
TP16 same freq at 50mv got .1v p-p

Q70 pin 1 is 0.65v
pin 2 - 0 volts
pin 3- 1.7 v

Q71
pin 1 - 2.06v
pin 2- 1.38v
pin 3- 4.48

Q72
pin 1- 5.66
pin 2 - 5.07
pin 3 - 11.92

Q73
pin 1 - 4.46
pin 2 - 5.07
pin 3 - 0.00

Measuring in circuit so might be off:
R72 shows on the schematic as 10k I measure 2.2k it's 103 so should be 10k
R73 shows 1.79k supposed to be 2.2k

Rob,
Thank-you for verifying that the connections as shown do work.? Would you know the reason for C211 in the original circuit?? I would have thought that Ashhar Fahran would have only installed one if the other was not needed.

73
Evan
AC9TU

Scrape off the toplayer of the underlaying trace and solder them there.
Works fine.
Rob PA0RBL

On 12/24/2018 12:31, d balfour wrote:

Woody
Did you every science out why the power seems low?

Have you tried an alternate mic?

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I have not yet tried to trace the signal path or a different microphone.?? Output power varies by band.? Strangely, it is lowest on 40M and 80 M, at 3-4 watts.? On 30M the power increases to over 10 watts.? From 30M up, the power decreases slightly (as expected) to about 7 watts? at 10M.

This happens with both SSB and CW.? Power is generally lower with SSB but the trend is the same.? I have my rig set up for digital / PC sound card feed also.? I can over drive with the sound card if I try, so do not think audio level is the issue.

Given the symptoms, I think the loss is likely in the output filters.?? I need to open the box and trouble shoot more!

Woody - KZ4AK

Thanks Evan I was not understanding that but got it now.? Appreciate all the great info and ideas/diagnostics here.

TP17 at 11.99 or so I could get a tone 480mv gave .1v p-p
TP16 same freq at 50mv got .1v p-p

Woody
Did you every science out why the power seems low?

Have you tried an alternate mic?

Too bad Evan. Your loss.

Your question made me go back and look at the picture.? L5 looks correct, as it is in the circuit as was the original (L5 and C215 in series with the filter).? L7 is directly connected to T4, removing C211 from the circuit.? Not sure if that is intentional, so good question!

Hopefully someone can answer your question, I do not know for sure.? Based on the values, I would assume that it is for DC blocking that may not be needed on both sides of the filter.

Evan
AC9TU

I tested with an RF Explorer SA and found that I had the harmonic issue on 40m, even on ssb.? I did not see the issue on 20m or 10m.? I have not had any success with those bands, mostly due to conditions.

I need to replace the relays and verify again before I use 40m.? I do not have an antenna for 80 (MFJ-2010 40, 20, and 10 only).? I could do 20m, however the band has been pretty bad over the past month, so now is the time to replace the relays.

73
Evan
AC9TU

Dave,
By the time the signal from the antenna gets to TP17, it has been converted to the audio on a 12mhz carrier.? Said another way, the signal by now has been converted to 12mhz +- the audio tone, not the base? original received frequency.

Injecting a pure 12mhz signal at TP17 (or TP16) should produce an audio tone that is 12mhz - the BFO frequency at TP20 (input to the audio amp).? From previous posts I believe that you stated the BFO as 11.996 mhz so you should have an audio tone of 4khz at TP20.

Evan
AC9TU

AT 60mV you should a really loud sound from your speaker. Check all the resistors and report on
DC voltages at the audio transistors.

Raj