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First contact today, slightly off frequency?

 

I made my first contact as a General today at 5pm PST. I was excited after countless times trying to make contacts, (even on BITX QSO Night). I never could until a station 100 miles North of me heard me calling him today.?

My BITX40 was on 7.2200. He told me that he was hearing me clearly on 7.222 I believe (the band wasn't too good). He told me that I should get a frequency reader to see how off I am.?

My question is, is there an easy way to fix this, and what is the problem here?
 

The easiest way is to find a frequency with regular activity. Most of the time they will be on exactly 5khz steps. Set your frequency on that exact step. Then put it in calibration mode, and tune back and forth until they sound normal in tone. Then disconnect the calibration wire to save the frequency offset. If you have another transceiver that is calibrated, with a dummy load you could tune for it's signal, or a friends calibrated signal. And use them for calibrating your display with the frequency you are on.

Check the wire up directions. I feel like I am not being clear enough. That's my fault. It's been a while since I calibrated mine.
 

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Congratulations! We all remember that first HF contact. Really fun stuff.

Have you done the calibration recommended? If not the BITX can be off a bit until you do so. Details are in the Arduino sketch but basically tune to a signal that you know the frequency off and then set the calibration. After that it will be correct. I used? a net that I know the frequency of and I know the voices of the net control so it makes it easy.

Have fun!

On 5/29/2017 7:17 PM, Daniel Acevedo wrote:

I made my first contact as a General today at 5pm PST. I was excited after countless times trying to make contacts, (even on BITX QSO Night). I never could until a station 100 miles North of me heard me calling him today.?

My BITX40 was on 7.2200. He told me that he was hearing me clearly on 7.222 I believe (the band wasn't too good). He told me that I should get a frequency reader to see how off I am.?

My question is, is there an easy way to fix this, and what is the problem here?

 

Thanks guys. Just to make sure, you both speak of this?



I have a pretty good ear and I know how to "zero" in on them. Most of the guys I hear talking are on 5khz steps like John said, and they are normally on an even number. 7.280 is always heard around here.?

Is this the 8 pin connector referred to in the "Wire Up"?

If so, I assume the only red wire is the one mentioned. Also, Can I just short this red wire to the battery of my BITX40??

calibration.png

 

In the good old days before digital readouts on radios transmitting on 7.222 MHz would not get a comment, now if your frequency dos'nt end in a 0 or a 5 you are accused of being off frequency.... maybe we should throw out our vfo rigs and go back to crystal control.....?
--
Mike VK3XL
 

Yes that't the right connector, short the red wire to ground to go into
calibration mode.

Alternatively, if you install the latest raduino sketch, you can do the
calibration from the front panel via the Function Button menu. Then you
won't need the red wire anymore.

73 Allard PE1WNL

On Tue, May 30, 2017 05:35, Daniel Acevedo wrote:
Thanks guys. Just to make sure, you both speak of this?

I have a pretty good ear and I know how to "zero" in on them. Most of the
guys I hear talking are on 5khz steps like John said, and they are
normally on an even number. 7.280 is always heard around here.??

Is this the 8 pin connector referred to in the "Wire Up"?

If so, I assume the only red wire is the one mentioned. Also, Can I just
short this red wire to the battery of my BITX40?
 

hi
does it actually matter that your frequency display is slightly off. As long as you are transmitting and receiving on the same frequency as you contact station then all is well.

terry gm4dso
 

True for normal SSB operation.
But it can be fixed easily so why not.

For certain digital modes exact frequency display may be crucial.

73 Allard PE1NWL

On Tue, May 30, 2017 10:15, terryhugheskirkcudbright via Groups.Io wrote:
hi
does it actually matter that your frequency display is slightly off. As
long as you are transmitting and receiving on the same frequency as you
contact station then all is well.

terry gm4dso
 

hi allard

the problem that i have had with calibration is finding a carrier on an exact frequency

i live in the sticks so finding a local station is hard to come by

73 de terry gm4dso
 

I hear you loud and clear. Even if it's not a 0 or 5.
Ken,T
 

Terry,

Here's another trick:
in the evenings there are quite a few strong broadcast stations in the
section above 7200 kHz. You should be able to hear them even when you live
"in the sticks".
As these are broadcasting an AM signal with unsuppressed carrier you can
use them for calibration your radio.
Broadcast stations are usually precisely on frequency at 10 kHz intervals.
You will hear a strong whistle when you tune to a broadcast station. As
you tune trough the signal, the pitch of the whistle will go from high to
low until it is zero and then go up again.
The point where the whistle is exactly zero Hz is "zero beat". You can use
this as a reference point for calibrating your radio. In calibration mode,
adjust the offset value so that the whistle is zero Hz.

73 Allard PE1NWL

On Tue, May 30, 2017 12:13, terryhugheskirkcudbright via Groups.Io wrote:
hi allard

the problem that i have had with calibration is finding a carrier on an
exact frequency

i live in the sticks so finding a local station is hard to come by

73 de terry gm4dso
 

Use a website like websdr.org to tune into a strong broadcast, and then try to find that same broadcast on your bitx.

Of course, this assumes the SDR station is showing the correct frequency.

Alternatively, if you do make contact with someone who has a more precise rig, ask them what their exact frequency, then use that information to calibrate.
--
Darren, W9ZIM
Guy N7BIR
 

Another good way to do the calibration is to purchase one of the little inexpensive Pixie QRP transceivers. It puts out a CW carrier on 7040 MHz. Makes for a cheap signal generator. ?You can find them on Amazon and EBay.?
 

I sincerely doubt the crystal used on an $3 ebay Pixie would be any more accurate than the crystals used on the Bix40.?

Allard's suggestion of calibrating to one of the SW AM Broadcast stations is a good one, as broadcasters are almost always on 10khz increments. ?All AM SW Broadcasters should be above 7.2mhz, and all their images should be below 7.2mhz, ?avoid using those images. ?The tuning knob will tune through an image 4 times as fast as a normal signal since it is received using the 4'th harmonic of the VFO.

If we assume the 25mhz crystal in the Raduino and the 12mhz BFO crystal on the Bitx40 main board are both correct within 100 parts per million, we might have as much as 200ppm error on a stock Bitx40. ? ?200 ppm at 7mhz is 200*7mhz/one-million = 1400 hz. ? Most rigs should start out much closer than that, so will be easy to tell which 10khz increment some SW Broadcaster is on.?

From post 25393: ? "In addition to the 7.2mhz birdie, we also have a problem with images from SW broadcasters getting through due to the 4'th harmonic of the VFO mixing with the incoming signal. ?For example, when receiving at 7.1mhz, the vfo is at 12-7.1 = 4.9mhz, the 4'th harmonic of which is 4.9*4 = 19.6 mhz. ?That 19.6 mhz is present in the diode ring mixer, and mixes with a signal at 7.6 mhz to create a 12mhz if signal."

Jerry, KE7ER


On Tue, May 30, 2017 at 10:39 am, Guy N7BIR wrote:
Another good way to do the calibration is to purchase one of the little inexpensive Pixie QRP transceivers. It puts out a CW carrier on 7040 MHz. Makes for a cheap signal generator. ?You can find them on Amazon and EBay.?

?
 

Correction: ?The SW Broadcasters are assigned frequencies on 5khz increments. ?But a stock Bitx40 should still be accurate enough to know which 5khz step the broadcaster is on.


On Tue, May 30, 2017 at 11:28 am, Jerry Gaffke wrote:
as broadcasters are almost always on 10khz increments.

?
OZ9AEW
 

another possibility is found your frequency counter and use the attached Skecth and simply hardcode you freq !
in my case it was 25.0053MHz

calibrate_rarduino.ino
calibrate_rarduino.ino

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