Amateur Radio Parity Act Reintroduced

ARRL Bulletin 14  ARLB014US_Capitol
From ARRL Headquarters
Newington CT  March 9, 2015
To all radio amateurs


The Amateur Radio Parity Act of 2015 Introduced in Congress

“The Amateur Radio Parity Act of 2015” – H.R.1301 – has been introduced in the US House of Representatives. The measure would direct the FCC to extend its rules relating to reasonable accommodation of Amateur Service communications to private land use restrictions. US Rep Adam Kinzinger (R-IL) introduced the bill March 4 with 12 original co-sponsors from both sides of the aisle – seven Republicans and five Democrats. Kinzinger also sponsored “The Amateur Radio Parity Act of 2014, which died at the end of the 113th Congress. H.R. 1301 is an essentially identical piece of legislation. Continue reading “Amateur Radio Parity Act Reintroduced”

Adafruit Si5351A 3-Channel Clock Generator

DSC00553_scaledThe other day, I received a breakout board for this critter from Adafruit. I want to experiment with RF applications, in particular an Arduino-controlled VFO. For this purpose, I need to be able to set the PLL and divider parameters in real time on the fly in response to, for instance, the turn of a rotary encoder, or direct keypad entry. The Arduino library provided by Adafruit is good for firm-programed parameters, but not for run-time settings.

I’ve done a pretty-good search through the Silicon Labs site and all I found was their Windows app for calculating those parameters for static programing–not for on-the-fly applications. I was hoping to find some formula or algorithm for determining the parameters given a specific frequency to be generated.

After what Lady Ada (Limor Fried) calls “noodling around,” I found a number of Arduino libraries for the 5351 at GitHub. Except for Adafruit’s own respository there, everything else is RF/Ham radio focused. So far,  I’ve experimented with a library developed by Jason Milldrum NT7S for his IndieGoGo Si5351A breakout-board campaign. I found it works flawlessly with the Adafruit breakout as well.

The nice thing about Jason’s library is that it will calculate the PLL and divider frequencies from an output frequency specified by a variable. This is exactly what I wanted. With a few buttons and a rotary encoder or keypad, I can dial in the frequency I want.

Here’s Jason’s GitHub respository:

Adafruit Si5351A Breakout Board w/ArduinoI have yet to explore all the features of the library, but so far I’ve used a variable that allows the xtal-load capacitance to be entered–no doubt to fine-tune the calculation of PLL and divider frequencies. According to the Adafuit document, 10pF is the nominal figure. That’s what I used and it got the closest to the specified output frequency of those I tried.

Another feature I’ve noticed but not yet tried is a variable to enter a correction factor to compensate for manufacturing tolerances of the 25MHz reference xtal. Before I try that, I need to setup a GPS-disciplined frequency standard to properly calibrate my gear.

One odd thing I’ve found is that the official Silicon Labs datasheet for the Si5351A/B/C series lacks information on pinouts–by pin number, that is. They show pin names but no numbers. Strange! I finally found them, though, on Lady Ada’s drawing.

The cool thing about the Si5351 is that it can generate both the VFO and the BFO frequencies for a receiver/transceiver at the same time. If the rig needs a digital clock for other purposes, the 5351 can provide that as well.

As you can see from the waveform on the ‘scope screen, it’s not a perfect sine wave. This is to be expected, and a simple low-pass filter (LPF) can clean it right up.



Here’s the link to Adfafruit’s page for the breakout board:

At $7.95USD, it’s an excellent buy, especially considering it includes pull-ups and a LDO regulator so either 5V or 3.3V can be used for power and pin-high levels.

I’ll report more on the Si5351A in general and the Adafruit breakout in particular in subsequent postings.



!!! THIS JUST IN: I also just received my “perk” for my contribution to NT7S’s IndieGoGo campaign for his Si5351A breakout board. It’s comes as a kit, so I’ll assemble it and post a preliminary report soon.

Antenna Raising Weather is Here!

“The best and most expensive transmitter is but a useless toy if it is connected to a poor antenna.”                                                                               

Bill Orr, W6SAI, S-9 Signals (1959)


Green grass, mild days, and blue skies are sure signs it’s time to climb towers, string wire, and get up on rooftops in the never-satisfied quest for a few more dB of gain.

It’s also time for contest pallor and seasonal-affective disorder to give way to tanned skin and spring fever. IOTA, SOTA, and POTA (Islands, Summits, and Parks on the Air, respectively) activations seem alluring again. Two-meter radio direction finding and foxhunting offer fresh air and at least a little exercise.

It’s good weather to grab your QRP field bag and head to the local park or lake, toss a EFHW antenna up in a tree, and attract both QSOs and curious onlookers. You can boast how many hundreds of miles per watt you get from that little cigarette-pack sized rig.

Hunting for the source of that new and pesky S7 noise floor in your otherwise-quite neighborhood now takes on the grim-yet-determined character of a military campaign.

Marred only momentarily by the tax-filing deadline, Spring is always something of a happy surprise.

Radio Crystals Developed during War

Here’s a very cool post on the development of radio-crystal manufacturing during the Second World War. Xtals had been used experimentally before the war, but the need for reliable communication transformed amateur radio based mostly on coil and capacitor oscillators to the widespread use of much-more stable crystal ones.