Skip to main content

Sept 25, 2024. One of the best LC VFO's

Those several words: N6QW and LC VFO's said in the same sentence are much akin to wearing Brown Shoes with a Black Tuxedo.


But if you are so inclined to use Analog VFO's then hunt and find an Analog VFO assembly from one of the early Yaesu Radios, like the FT-101. The unit is small, but more importantly is linear, stable and clean! Yaesu found the magic decoder ring. I have two Yaesu radios (FTdx100 vintage 1967 and a FT-101EE vintage late 1970's) and both VFOs are just as I described.

One of my more successful radio projects was the JABOM* which originally started life as a 17M radio with a homebrew 4.9152 MHz Crystal Filter and VXO. In the Rx Tx Mixer Module, I had two sets of BPF's so with a pin header and Jumper pins I could add in 20M.

That worked OK except I got a critical report from someone I trust who said my LSB component was only down about 25 DB. He is an RF Engineer and could actually look at my signal with test gear he has in his shack.

That did it! I ripped out the homebrew filter, installed an 8.998500 BFO and added a 9 MHz commercial filter and wired everything for 20M. The real plus for this rig was the HyCas IF and AGC. I ditched the VXO and because I had a Crystal BFO the DDS of the day was the AD9850 and that is what went into the radio. 

The AD9850 was a predecessor to the Si5351 and was only good to 40MHz and did not have the capability to generate two separate frequencies. Its output needed filtering and could be somewhat tepid. 

So, after 15 years I embarked on replacing the AD9850 with the Si5351. The current approach with my Si5351 is to have two frequency ranges and VFO memory. So, the replacement unit boots up on either 14.2 or 14.074. A simple toggle switch enables jumping back and forth. If the SSB part of the band sounds dead, I need only flip the switch to see if there are FT8 signals and usually there are. 

Here is a brief snippet of the 1st rough checks to see if we have it working.


Once again building in modules facilitates major changes. It also works well with my limited time available. I had the AD9850 out of the JABOM in about 3 minutes. Luckily, I have a box full of Arduino/Si5351 assemblies wired up and so about the same amount of time to pop in a unit to run some tests. This looks promising. 

TYGNYBNT. Don't eat your pet.

* JABOM = Just A Bunch Of Modules.

73's
Pete N6QW


Popular posts from this blog

January 26, 2024. A simple CW Transceiver/Transmitter

Cruise through the lower part of the ham bands bands and what do you hear? Well, FT-8 and CW. Often you will not hear any SSB stations yet go to the lower part of the bands, and it is a cacophony (I love that word) of bad sounding signals and some high-speed keying. Fast is not so much of the issue as is bad, run together and jerky keying. But none the less our hobby started there.    So, you could crank down your ICOM 7300 and watch the waterfall on CW or you could homebrew a radio. Actually, to do CW right you need more thought up front than you do with a SSB transceiver. Often, I will state that a CW Transceiver is much more difficult to build than a simple SSB rig. I published two articles in QRP Quarterly on CW transceivers and all I got was a yawn so maybe history will repeat itself.  Yawn!   30M CW Transceiver with RIT!   Of interest is that the LO is a Varactor tuned LC oscillator using a NE602. Look closely at the RIT circuit which is only activated on ...
Read more

March 31, 2024. Happy Easter to those who celebrate this day.

What a great day to Binge on Chocolate and experience the pain of that filling that has been leaking.  I would be in that category with the leaking filling(s) had I not just spent an amount equivalent to one of the fancy new uptown appliance box transceivers on two filling repairs. Well at least I can binge on the Chocolate bunnies without fear of pain. Regrettably everything appears to have jumped in price including the price of parts. Well not so much the parts as the shipping costs.  That notably is seen in the eBay treasures. I spotted a nice heathkit DX-20 for about $50 and the shipping was $65. Likely it is a twofer with part being a way to in effect charge a higher price by inflating the shipping and in part by increased shipping costs. Shipping with insurance across the US was about $150 for this jewel and that was three years ago. 6AM on the Left Coast ~ 20M Easter Sunday! My only hope is the cost of Chocolate Bunnies remains steady although a pound of See's Candies f...
Read more

August 30, 2024. A PNP 20M SSB Transceiver

Shown below is the Block Diagram for the 20M PNP SSB Transceiver steered in the  Transmit Mode . The components shown in the dotted block are relay steered so that the block module is single pass and amplifies in a single direction. The Block diagram show steered in Transmit.  Essentially the steering process works so that the IF Module input follows the Balanced Modulator on Transmit and then the input side follows the Receive Mixer on Receive. All done with some relays and a bit of RG174U coax. For those who count things in detail, this block diagram is not unlike what was used for the PSSST Transceiver which can be found on my website . Yes, a warmed over P3ST only using PNP devices. TYGNYBNT. 73's Pete N6QW
Read more