Messages

1

General Radio Discussion / Re: Are there no radio laws in Greece?

« on: October 07, 2019, 0214 UTC »

Most countries don't seem to care too much what kind of radio equipment that you might manufacture and sell as EXPORTS...

This is profound and I LOL'd

2

Equipment / Re: New T2FD Antenna Construction and Performance

« on: August 27, 2019, 1348 UTC »

it is often because a knot is hitting a branch

In cases like these I send a "carrier wave oscillation" up the rope orthogonal to the plane of the branch and rope.  This can "jump" the knot over the branch, however these operations have always been within 40'.  I doubt I could get the wave to travel all the way up 80' with enough amplitude to jump the knot over. 

3

Propagation / Re: Attention Propagation Nerds

« on: August 19, 2019, 0152 UTC »

solar-cycles-explained-by-planetary-alignment

This is the dawning of the Age of Aquarius, Age of Aquarius......

4

Equipment / Re: New T2FD Antenna Construction and Performance

« on: August 07, 2019, 1933 UTC »

I've tried using a slingshot and fishing wire to get rope up high, and it doesn't work out well for me. Do you have any advice in this regard?

5

Equipment / Re: New T2FD Antenna Construction and Performance

« on: August 07, 2019, 1200 UTC »

How does the T2FD noise floor compare to other antennae, such as your groundloop, skyloop, bev, perhaps if you have an active type. Say noise floor of each and signal level of the same signal on each ant at or close to the same time.

Enquiring minds want to know. I intend to raise a dedicated SWL antenna this fall along the edge of my property. The engineering and logistics of a T2FD is higher than for a dipole. Is it worth it?

6

The RF Workbench / Re: Loop Stick Ferrite Physical Connections

« on: August 05, 2019, 2100 UTC »

The paper goes on to discuss leakage flux, and says that with a short coil on a long rod, Q and inductance are maximized with the coil centered on the rod.  If the coil is extended to the length of the rod, Q will go even higher but inductance will drop.  This can be fixed by adding turns on the rod.

7

The RF Workbench / Re: Loop Stick Ferrite Physical Connections

« on: August 05, 2019, 2045 UTC »

I was doing some more loop research and found a good read:

https://pdfs.semanticscholar.org/4736/4a3b4a94109482271f3ff3d249d780acac23.pdf

It's the first time I've encountered a description of how ferrite actually increases signal pick up:

"If an air-core loop is placed in a field, in essence it cuts the lines of flux without disturbing them. On the other hand, when a ferrite (magnetic) core is placed in the field, the nearby field lines are redirected into the loop. This is because the reluctance of the ferrite material is less than that of the surrounding air, so the nearby flux lines tend to flow through the loop rather than passing it by."

It essentially bends more of the M component lines of the RF wave into the loop, wild stuff!

8

Equipment / Re: AcuRite 02020 Portable Lightning Detector

« on: August 02, 2019, 2223 UTC »

I suspect the algorithm is what makes this stand out from an untuned AM radio. When I was researching roll-your-own loopstick antennas, one of the most informative posts I found was at a WX forum with a bunch of guys building lightning detectors. I read through a bit and it looks like these things are more complex than simple static detection in low bands.

I was a lifeguard at my county waterpark years back, and they had one that certainly cost more than $25. The art isn't detecting lightning somewhere on your half of the country, as mentioned here, but rather to detect when lightning is close enough to be dangerous. The park lost revenue if there weren't bodies in the pool, so precision was worth the premium.

9

Longwave Loggings / Re: Summer 2019 NDB Logs

« on: August 01, 2019, 2043 UTC »

It's local for me, too, and the fact I didn't hear "EN" upfront suggests my ears need far more Morse training.

I've read your build log with some fascination.  I'm not currently up to the task of regen loops, but I'm starting into a remote tuned loop. I'm planning to purchase a handful of NTE618 varactors, unless you can recommend newer part.

I'm thinking of using this for the voltage control:

https://www.ebay.com/itm/LM317-AC-DC-Adjustable-Voltage-Regulator-Step-down-Power-Supply-Module-with-C7A4/352674072655

10

General Radio Discussion / Re: Estonian electronic warfare

« on: August 01, 2019, 1701 UTC »

Do you suppose anyone uses non-digital non-encrypted non-skip comms during war anymore?

11

Longwave Loggings / Re: Summer 2019 NDB Logs

« on: August 01, 2019, 1659 UTC »

I'm just starting into this now, and last night had 389 EN Kenosha, WI booming in. 

Is it just me, or is beacon Morse whack?  I couldn't ID "EN" for a bit because it sounded like either "ETE" (. - .) or "R" (.-.).  I can't detect a spacing between "E" and "N" (. -.).

12

Amateur Radio / Re: 14.230 - to phone or not to phone?

« on: July 31, 2019, 2212 UTC »

W4AQL (Georgia Tech) is operating on 14.233 right this moment.

13

General Radio Discussion / Re: Estonian electronic warfare

« on: July 31, 2019, 0253 UTC »

That R-148 portable looks awesome, sorta like that 70s 6m portable mentioned here not too long ago.

14

Equipment / Re: New T2FD Antenna Construction and Performance

« on: July 29, 2019, 1753 UTC »

Since reading this thread I've been giving the T2FD some serious consideration and research.  Of particular interest is the function of the resistor at the "far end" of the antenna.  Understanding its purpose should help in designing my own T2FD.

I found a very old post from this very forum describing (at least a portion) of the resistor's function which suggests why so many report the TF2D as having lower noise and better S/N than monoband dipoles:

The balancing resistor keeps the elements in perfect balance all the time in relation to the feedpoint, and THAT does a very effective job of canceling out local noise.

Having read elsewhere that "dummy loads have extremely flat SWR curves" and noting the T2FD is very wide-banded, the concern is how much energy is lost and how to minimize it.  The same post from above includes this:

In addition, at MOST, the balancing resistor might cause a 3 dB drop in signal (1/2 an S-unit).  Most of the time, it absorbs little, if any signal.  Almost all signal is fed to the feedpoint through the folded dipoles because of the slightly lower resistance at the feedpoint that at the balance point.  That is why for a 500 ohm feedpoint, you use a 540 to 600 ohm resistor in a terminated folded dipole.

As noted elsewhere in this thread, good performance from a T2FD depends heavily on the resistor value.  The above post gives an explanation for why that is.

Is finding the feedpoint impedance simply a matter of deploying a T2FD, running the shortest possible 50-ohm coax to an analyzer and noting the R in an R,X scan?

15

Amateur Radio / Re: 14.230 - to phone or not to phone?

« on: July 29, 2019, 1413 UTC »

I was looking at this:

https://wireless2.fcc.gov/UlsApp/UlsSearch/license.jsp?licKey=764946

I suppose I don't understand how the FCC DB works.