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Author Topic: Inexpensive signal sources for CW transmitters  (Read 1052 times)

Offline Teotwaki

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Inexpensive signal sources for CW transmitters
« on: August 22, 2018, 1725 UTC »
I've been watching the various flavors of Chinese direct digital synthesizers (DDS) on eBay and you can get a lot of capability for low prices.

Rather than order a crystal from some slow and traceable source you can use one of these to easily choose a frequency for the HF bands

Sorting through the Ebay listings is a pain as the sellers are rarely technical enough to understand what they are selling. The product's description can range from fair to terrible to non-existent.

example:

DDS Function Signal Generator Module DDS Sine Square Sawtooth Triangle Wave

https://www.ebay.com/itm/DDS-Function-Signal-Generator-Module-DDS-Sine-Square-Sawtooth-Triangle-Wave/181860086069?_trkparms=aid%3D444000%26algo%3DSOI.DEFAULT%26ao%3D1%26asc%3D53210%26meid%3D91104aba5aa042f2a34bcc78c75eaffe%26pid%3D100752%26rk%3D2%26rkt%3D6%26sd%3D171928942747%26itm%3D181860086069&_trksid=p2047675.c100752.m1982

Features:

Main AVR DDS V2.0 signal generator features:

Dedicated high speed (HS) signal output up to 8MHz;
DDS signal with variable amplitude and offset;
DDS signals: sine, square, saw, rev saw, triangle, ECG and noise.
216 LCD menu;
Intuitive 5 button keypad.
Frequency adjusting steps: 1, 10, 100, 1000, 10000Hz;
Restores last configuration after power up.

You could unplug the circuit board's display to save a bit of power when it is operating unattended..

The DDS is the green circuit board in the lower half of the picture.


YouTube video review  https://www.youtube.com/watch?v=2zojBi2fvwU

The reviewer points out some design flaws but for under $14 it is hard to complain.
Jim
NRD-525, Elecraft KX3 and Elecraft PX3 Spectrum Display
76' end fed long wire & 66' off-center fed dipole for 10/20/40 meters
Orange County, SoCal, The better half

Offline JimIO

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Re: Inexpensive signal sources for CW transmitters
« Reply #1 on: August 22, 2018, 1859 UTC »
That one is not an RF DDS. I got one of those before knowing that. The HS output is a square wave derived by dividing the clock so its only 16Mhz/n. 1,2,4,8Mhz.
The other output only goes up to 50Khz I think. I never built it and don't have the specs handy. What you want to look for is something based on an AD9850 or AD9851.

Offline JimIO

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Re: Inexpensive signal sources for CW transmitters
« Reply #2 on: August 22, 2018, 1959 UTC »
A good place to look for crystals is "radio 741 rf and microwaves" on ebay.

Offline ChrisSmolinski

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Re: Inexpensive signal sources for CW transmitters
« Reply #3 on: August 22, 2018, 2014 UTC »
I built an AD9851 based DDS kit several years ago: http://www.radiohobbyist.org/blog/?p=73
Chris Smolinski
Westminster, MD
eQSLs appreciated! csmolinski@blackcatsystems.com
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Offline Teotwaki

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Re: Inexpensive signal sources for CW transmitters
« Reply #4 on: August 22, 2018, 2057 UTC »
I actually have one of these assemblies (UDB-1005S) pictured below. It is the 5MHz version for $30 and I have it outputting 4 MHz at the moment

https://www.ebay.com/itm/UDB1005S-Function-Signal-Generator-Source-Frequency-Counter-DDS-Module-Wave-5MHz/321418276142?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649



So if the one in the first post can only output in the 50 KHz range then this flavor of DDS is better for the hobbyist a little higher cost. They also sell 8 MHz and 10 MHz output versions for a bit more.
Jim
NRD-525, Elecraft KX3 and Elecraft PX3 Spectrum Display
76' end fed long wire & 66' off-center fed dipole for 10/20/40 meters
Orange County, SoCal, The better half

Offline Stretchyman

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Re: Inexpensive signal sources for CW transmitters
« Reply #5 on: August 22, 2018, 2149 UTC »
Yes! Xtals still on the Agenda..Still!

I'd offered an Xtal replacement (posted on here) some years back....Zero interest.

Have Times Changed Yet?.....

The AD9833 PCBs on eBay make a neat 'programmable Xtal' and that's what I currently use.

Str.
'It's better to give than receive' so why RX when you can TX!

                            Buy one from me, NOW!

Great discounts on ALL my transmitters if purchased via HFUnderground


                                              ;)

Offline JimIO

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Re: Inexpensive signal sources for CW transmitters
« Reply #6 on: August 22, 2018, 2253 UTC »
That would make a nice piece of test bench equipment for the money but seems like overkill for just generating a CW signal. You could buy a 22 meter beacon kit from Chris for $20 and a HC-49S crystal assortment from ebay for ~$9. Then you can pick from these frequencies:

3.6864MHz      HC-49S    2 Pcs
4.000MHz    HC-49S    2 Pcs
4.032MHz     HC-49S    2 Pcs
4.096MHz    HC-49S    2 Pcs
4.194304MHz    HC-49S    2 Pcs
4.9152MHz    HC-49S    2 Pcs
6.000MHz    HC-49S    2 Pcs
7.3728MHz    HC-49S    2 Pcs
8.000MHz    HC-49S    2 Pcs
10.000MHz    HC-49S    2 Pcs
11.0592MHz    HC-49S    2 Pcs
12.000MHz    HC-49S    2 Pcs
12.288MHz    HC-49S    2 Pcs
13.56MHz    HC-49S    2 Pcs
14.7456MHz    HC-49S    2 Pcs
16.000MHz    HC-49S    2 Pcs
18.432MHz    HC-49S    2 Pcs
20.000MHz    HC-49S    2 Pcs
22.1184MHz    HC-49S    2 Pcs
24.000MHz    HC-49S    2 Pcs
24.576MHz    HC-49S    2 Pcs
25.000MHz    HC-49S    2 Pcs
27.000MHz    HC-49S    2 Pcs
27.12MHz    HC-49S    2 Pcs
30.000MHz    HC-49S    2 Pcs
32.000MHz    HC-49S    2 Pcs
32.768MHz    HC-49S    2 Pcs
40.000MHz    HC-49S    2 Pcs
32.768KHz 2*6    2*6    2 Pcs
32.768KHz 3*8    3*8    2 Pcs

There is also 9.000MHz and maybe some others

Offline Teotwaki

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Re: Inexpensive signal sources for CW transmitters
« Reply #7 on: August 24, 2018, 1958 UTC »
I built an AD9851 based DDS kit several years ago: http://www.radiohobbyist.org/blog/?p=73


That was a neat project! With the chip based computers the DDS no longer has to have a cable to a desk top. Did your project evolve beyond what you posted?
Jim
NRD-525, Elecraft KX3 and Elecraft PX3 Spectrum Display
76' end fed long wire & 66' off-center fed dipole for 10/20/40 meters
Orange County, SoCal, The better half

Offline Teotwaki

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Re: Inexpensive signal sources for CW transmitters
« Reply #8 on: August 24, 2018, 1959 UTC »
Yes! Xtals still on the Agenda..Still!

I'd offered an Xtal replacement (posted on here) some years back....Zero interest.

Have Times Changed Yet?.....

The AD9833 PCBs on eBay make a neat 'programmable Xtal' and that's what I currently use.

Str.

Will go take a look for it
Jim
NRD-525, Elecraft KX3 and Elecraft PX3 Spectrum Display
76' end fed long wire & 66' off-center fed dipole for 10/20/40 meters
Orange County, SoCal, The better half

Offline Teotwaki

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Re: Inexpensive signal sources for CW transmitters
« Reply #9 on: August 24, 2018, 2018 UTC »
That would make a nice piece of test bench equipment for the money but seems like overkill for just generating a CW signal. You could buy a 22 meter beacon kit from Chris for $20 and a HC-49S crystal assortment from ebay for ~$9. Then you can pick from these frequencies

---SNIP----

I really like the simplicity and frequency agility of the DDS and the cost is really not much.

It is always good to post links to items that are mentioned.

Chris' kit is here - https://blackcatsystems.com/rf-products/22_meter_band_part_15_beacon_kit.html

Example of crystal kits on Ebay - https://www.ebay.com/itm/Crystal-Oscillator-HC-49U-HC-49S-Mixed-Assortment-Kit-10Values-50pcs/153135485798?hash=item23a7961366:g:9~MAAOSwZjJU7vUF

I could not find an Ebay store named "radio 741 rf and microwaves"
Jim
NRD-525, Elecraft KX3 and Elecraft PX3 Spectrum Display
76' end fed long wire & 66' off-center fed dipole for 10/20/40 meters
Orange County, SoCal, The better half

Offline Pigmeat

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Re: Inexpensive signal sources for CW transmitters
« Reply #10 on: August 24, 2018, 2108 UTC »
I built an AD9851 based DDS kit several years ago: http://www.radiohobbyist.org/blog/?p=73

I remember that paint can lid beauty.

I once saw a photo and schematic of a QRP amp using two IRF-510's  for 20 meters built on the bottom of a fairly new cast iron skillet. Something told me the guy had never been married? If he was, he got divorced shortly after that little trick. The kitchen utensils aren't to be used for moronic male impulses, trust me on that one.

My FIL once got into big trouble for trying to pan fry the Thanksgiving turkey before it was thawed. Before my time, but I knew I had a lifelong "Get Out Of Jail Free Card" after hearing the tale. How can you top an act like that?

Offline Teotwaki

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Re: Inexpensive signal sources for CW transmitters
« Reply #11 on: August 24, 2018, 2140 UTC »
I built an AD9851 based DDS kit several years ago: http://www.radiohobbyist.org/blog/?p=73

I remember that paint can lid beauty.

I once saw a photo and schematic of a QRP amp using two IRF-510's  for 20 meters built on the bottom of a fairly new cast iron skillet. Something told me the guy had never been married? If he was, he got divorced shortly after that little trick. The kitchen utensils aren't to be used for moronic male impulses, trust me on that one.

My FIL once got into big trouble for trying to pan fry the Thanksgiving turkey before it was thawed. Before my time, but I knew I had a lifelong "Get Out Of Jail Free Card" after hearing the tale. How can you top an act like that?

Well, a frying pan is a terrible heatsink! Something like a waffle iron could dissipate heat better, especially if the wife's hair dryer is used in the cool mode to blow air across the waffle iron grid   ;D



Jim
NRD-525, Elecraft KX3 and Elecraft PX3 Spectrum Display
76' end fed long wire & 66' off-center fed dipole for 10/20/40 meters
Orange County, SoCal, The better half

Offline Josh

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Re: Inexpensive signal sources for CW transmitters
« Reply #12 on: August 25, 2018, 1925 UTC »
I built an AD9851 based DDS kit several years ago: http://www.radiohobbyist.org/blog/?p=73

I remember that paint can lid beauty.

I once saw a photo and schematic of a QRP amp using two IRF-510's  for 20 meters built on the bottom of a fairly new cast iron skillet. Something told me the guy had never been married? If he was, he got divorced shortly after that little trick. The kitchen utensils aren't to be used for moronic male impulses, trust me on that one.

My FIL once got into big trouble for trying to pan fry the Thanksgiving turkey before it was thawed. Before my time, but I knew I had a lifelong "Get Out Of Jail Free Card" after hearing the tale. How can you top an act like that?

I don't think I can top that but one time tried to fry some just caught fish in the skillet, poured the oil into the pan, and shortly the fish started levitating above the pan by several inches! Looked at the oil bottle and it said Karo syrup.
Conveniently located near Vincennes Indiana.

Offline Pigmeat

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Re: Inexpensive signal sources for CW transmitters
« Reply #13 on: August 25, 2018, 1941 UTC »
My wife keeps the cooking oil and the Kayro syrup next to each other by the sink. I can't tell you how many times I've come to making that same mistake. It looks almost exactly the same.