Tag Archives: Homebrew

Ed’s Homebrew Fruitcake Tin Radio

Many thanks to SWLing Post contributor, Ed Ganshirt, who writes:

I had an old car radio from the 1940’s I salvaged the parts from, and a rudimentary schematic to build by. I decided to re-assemble in the container I stowed away the parts in. Nothing special just another AM broadcast radio in an unusual cabinet (fruitcake tin.)

I love it, Ed! It’s like a broadcast band version of Rex’s Tuna Tin QRP radios!

It must have been a challenge to mount all of the components on that tin. So how does she play?

Post readers: please comment and consider sharing your homebrew project!

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Video: EB3DYW’s Homebrewed regenerative receiver

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While browsing a videos on YouTube, I stumbled across this demonstration of a brilliant little homebrewed regen receiver by Javier Guillaumet (EB3DYW):

Click here to view on YouTube.

What a beautiful little receiver!

Though I’ve build a number of receiver kits, I’ve never built one from scratch. Someday, I will muster up the courage and do so, though!

If you like home-grow regen receivers, you must check out Dave Richards’s Sproutie II regen receiver as well. A true work of art!

Post readers: Do you have any homebrew projects to share? Please comment!

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Dave builds an N6KR/Wilderness Radio SST from scratch

Guest Post: Building a magnetic loop antenna & broadband amplifier for your SDR

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Many thanks to SWLing Post contributor, Dave Gahimer (K9ZCE) for the following guest post:

Small Magnetic Loop Antenna with Broadband Amplifier for SDR Reception

by Dave Gahimer (K9ZCE)

Those with limited space, or antenna restrictions, might find a small 1 meter loop antenna a solution.

My son lives in an apartment. One Loop leaning against a wall gives him acceptable reception with the SDRPlay RSP on the ground floor–2nd or 3rd level flats should have very good reception.

Ten meters off the ground outside should give reception equal to any SWL antenna. We all with SDRs fight the image problem. Normal resonate ham band antennas show too strong reception of unwanted bands/stations. Did I mention noise? Loops are well known for –6 db noise reduction.

Then there is the possibility of SDR chip damage from your 1.5 KW station! In researching Loops we came across LZ1AQ. A Brilliant design /engineer (http://www.lz1aq.signacor.com/). Deep reading sometimes, but a great understanding of what makes a good receiving loop antenna.

Those who chase DX know that sometimes fading is caused by the signals’ polarization changing in the Ionosphere. Having both vertical and horizontal loops, and the ability to combine both signals diminishes this fading problem. Being able to filter the powerful, commercial FM transmitters diminishes image problems. Clipping strong signals at the antenna from very near powerful antennas/transmitters could save the SDR receiver from damage.

The LZ1AQ broad band Amp solves all these problems. http://active-antenna.eu/amplifier-kit/.

My son Ted and I built three, one meter loops from soft ½ inch copper plumbing tubing. One for his apartment, two for my crossed loops antenna. We weather proofed the Copper from corrosion by coating with outdoor clear spar varnish. We shaped the circle by drawing the tubing around a round glass top patio table.

The soft copper loop in held by white PCV plastic plumbing pipe. 1” or 1.25 inch schedule 40. Be careful to check that the PVC is schedule 40, thick wall. The thin wall pipe is not strong in the wind and will crack when you try to drill it.

Drill up to a 3/8 hole for the ½” copper tube to go through, then file out to fit. Here are some photos (click to enlarge):

Check out these links (all courtesy of LZ1AQ) to acquaint yourself with the loop construction and amplifier installation:

http://active-antenna.eu/tech-docs/2_ActiveAA_Mount_20.pdf

http://active-antenna.eu/tech-docs/1_ActiveAA_DandS_20.pdf

http://active-antenna.eu/tech-docs/3_ActiveAA_Antena_11.pdf

Many SDR receiver owners have seen improved noise and Image reduction by placing the plastic cased SDR unit on a small shielded/ grounded case.

The Amp needs 12VDC from in the shack. The Amp has two relays that you can switch, from in the shack, to select Vertical or Horizontal loops, or a dipole. The loop amp connects back to the shack via a shielded Cat 5 cable, Make sure you get shielded CAT 5 to reduce noise pickup. Make sure you provide an adequate good Ground below the antenna, less noise pickup and lightening protection.

Have fun!
Dave, K9ZCE
Retired from EE Dept @ Rose-Hulman Institute of Technology
Terre Haute, Indiana

Thank you so much, Dave!

Readers: yesterday I saw Dave’s loop antenna photos on the SDRplay RSP Facebook page. I was fascinated by his horizontally/vertically oriented loops and asked if he would write up a short guest post. He kindly obliged in a matter of hours!

If you have an antenna project you’d like to share, please contact me. So many SWLs and ham radio operators live in areas with restrictions and pervasive RFI–projects like Dave’s can revive one’s radio life!

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A simple homebrew high pass filter

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Many thanks to Jon Hudson, of SDRplay, who posted the image above along with the following note on Facebook:

David, WA7JHZ has designed and assembled this neat 2.6 MHz high-pass filter (HPF) for use with SDRs. He says that this simple input band-pass filter (BPF) might be of interest to anyone suffering from strong AM broadcast stations that are causing overloads…..David suffers from three nearby AM radio broadcast stations that overload the front ends of several of his receivers, including the SDRplay RSP and this is an ideal, low cost solution. He built this circuit from junk parts and commented that Amidon T44-2 iron powder cores would have made a better design, but that he decided to keep costs down with this design.

This design is simple enough for almost anyone to build and could help your receiver’s front end from overloading. Many thanks to David for the design/schematic and to Jon for sharing!

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Dave’s Sproutie SPT Beacon

Tony’s homebrew mag loop antenna and amplifier

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Yesterday, Tony (K3DY), shared a video (via Twitter) demonstrating his new home brew loop antenna and amplifier.

This is actually a great demonstration of how even a relatively simple, inexpensive loop antenna can improve reception in locations with heavy radio interference. Tony includes the following notes with his video:

“Testing a new receiving loop antenna that I built today. It uses a pre amplifier based on deferential setup of two 2N5109 transistors. Loop is made out of coaxial cable, only the shield is connected to the circuit.

Quick demo on 31 meters, lots of stations at sunset time. No time for further testing but I observed a pronounced directivity below 7 MHz. 75 meters is so quiet that it makes me forget I live in a townhouse. As a comparison, my noise level on 75 meters is at S8 on an end fed [antenna].

I will use this loop primarily for SWLing purposes but I may use it as a separate receiving antenna with my amateur radio equipment.

A lot of fun, loops are fascinating and efficient!

Indeed, Tony! And perhaps the icing on the cake is that loop antennas are so portable, low-profile and easy to deploy. They’re ideal for those living in restricted areas and with picky home owners’ associations.

Inspired by my buddy Vlado (N3CZ), I’ve actually been collecting the pieces to build my own mag loop antenna this winter. I doubt the parts for my loop will exceed ten dollars as I plan to use the shield of some heavy coax for the primary loop and a little PVC for support (much like Tony’s loop).

Tony’s video is inspiring me to go a step further and also build a simple amplifier. Any suggestions or schematics for doing so are most welcome!

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