Category Archives: Accessories

James adds an LM386 amplifier kit to his Heathkit GR-150

Many thanks to SWLing Post contributor, James Surprenant (AB1DQ), who shares this update to his review of the Heathkit Explorer Jr. TRF AM radio receiver kit:

With regard to the Heathkit TRF AM receiver kit, I did indeed build my LM386 amplifier.

I was planning on home-brewing it from scratch as the chip is pretty much all you need and there are various proven schematics for the circuit, but in the end I went with a small kit from Nightfire Electronics for $10 plus $5 shipping that I found on Amazon.com.

It was a bit cheaper to buy it in kit form, of course, and then there was the convenience of having all the parts in one place.

Here is a photo of the kit as advertised on Amazon…

And here is my build with the Heathkit…

I modified the kit to add a 3.5mm input jack, replacing the RCA jack that came with the kit, to make it easier to plug into the Heathkit radio.

I deliberated whether to install the audio amp into the Heathkit cabinet drilling out a couple of holes for the pot shafts. It all would have fit and I could have easily mounted the 3″ 8 ohm speaker to the back panel of the Heathkit radio. In the end, I decided to keep the radio original and mounted the amplifier board on a small piece of wood I found at a hobby store and decided to leave it all exposed. It works well, all things considered.

(Click here to view video on Facebook.)

It worked well and per my original review on SWLing Post, I feel Heathkit should have included such a little amp in the kit – it makes a big difference.

Many thanks for the update, James! That little LM386 amp kit seems like an affordable addition for any receiver lacking an amplifier or adequate audio amplification.

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Mike’s Virtual Audio Cable (VAC) promotion

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SWLing Post contributor, Mike Ladd, has been working with vendors to lock in promotional pricing on products and accessories commonly used by SDR enthusiasts. Last week, for example, he shared an excellent promotion for high/low pass filters.

This time, Mike has reached out to the author of Virtual Audio Cable (VAC) who has also kindly offered a discount.

VAC is a fantastic piece of software that allows you to port audio from one application to another on your PC without loss of audio quality. For example, if you’re running an SDR and you want to port its audio to FLDigi (to decode SSTV, RTTY, PSK31, or another digital mode) VAC does this for you.

Mike’s discount allows you to purchase a self-support copy of VAC for $21.42 US (a $3.78 discount).

To get the promo price, you’ll need to use this link which has the embedded coupon code, then simply make the selections as shown below:

Click here to purchase VAC with promotional pricing.

Thanks again, Mike, for sharing discounts with the SWLing and ham radio communities!

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Portable power for active antennas

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CPI1000 mit Powerbank

Many thanks to Dennis at Bonito for sharing a link to an article he recently published on the Bonito blog:

Autonomous power supply of our active antennas via USB and power bank

It is getting to be more and more difficult to procure reasonably priced analogue external plug-in power supplies because just like old light bulbs they are no longer allowed to be produced due to power consumption restrictions. We are spending a lot of time to find and buy remaining stock so that we can offer our customers noise-free external power supplies. But for years, there has been an alternative.

Our MegaLoop ML200, ML052, the MegActiv MA305 as well as the GigActiv GA3005 can be operated internally with as little as 5V and so can be powered by the supplied CPI1000DP / CPI3000DP bias tee via a USB cable. In light of the annoying switching power supplies, PowerLAN and heightened mobility of listeners, this is a very practical alternative and offers much more flexibility for the customer. Unfortunately, this fact is not well known and that is why I would like to shed some light on this subject.[…]

Continue reading at the Bonito website.

Thanks, Dennis!

I should note that there are a multitude of 5 VDC powerblocks on the market. I have two made by Eton Corp (see above) that even have hand-crank power generation. I recently used one to power my Raspberry Pi (Raspberry Pirate!) for several hours.

As Dennis states, using a DC source certainly cuts down on interference from noisy power supplies.

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Mike’s low and high pass filter deals

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SWLing Post contributor, Mike Ladd, is an avid SDR enthusiast and an administrator of the SDRplay Facebook group. Mike contacted me about special pricing he has arranged for low and high pass filters through Rescue Electronics. Mike explains:

These filters retail for $70.00 each. I spoke to the builder. I told him who I was and what I do and got him to make a deal for anyone in the United States with these filters and a direct link to his site. I make zero dollars on this. I always try to give back to the hobby and the community any way possible.

You have 3 choices: a high pass filter, a low pass filter, or a combo package.

These are hand built one at a time by Paul W1VLF with your choice of SO-239 or BNC connections. Full details are below:

High pass filter $55 shipped anywhere in the USA

This filter will begin attacking the AM band at 1770 Khz and increase attenuation as frequency decreases.

You can see this in the screen capture of the swept filter below.

160 Meters and above is virtually left untouched, but below that is where the attenuation takes place.

The filter has attenuated 60 db by 960 KHz.

The AM band has some very large signals that can mix in the front end of your. A lot of these spurious frequencies can land in 160 meter band or above.

For instance, I have a big signal at 1080 Khz and another at 770 Khz, add these 2 together and you get a spur that falls at 1850 Khz

Picture this happening at multiple frequencies with multiple mixes and you have a raised noise floor in the 160 Meter band.

The filter is built into a 2″ x 4″ 1.25″ 1/8″ wall aluminum enclosure for excellent RF shielding

Low pass filter $55 shipped anywhere in the USA

The AM-2 filter has a cutoff at 520 KHz.

Then, and without a lot of fanfare it begins the attack on the MW band.

Purchase this filter if you are into NDB, DX’ing, Maritime Mobile, Navetex, FCC Part 5 600 Meter band.

Each filter is handmade and swept in my lab.

The AM -2 Low pass is equipped with BNC connectors.

The filter begins to roll off at 520 Khz and gives an ultimate rejection of around 80 Db.

The filter is built into a 2″ x 4″ 1.25″ 1/8″ wall aluminum enclosure for excellent RF shielding

Combo deal for both $100 shipped anywhere in the USA

Click here to view/purchase via Mike Ladd’s promotional page at Rescue Electronics.

Many thanks for sharing this Mike! During my presentation at the Winter SWL Fest last week, I spoke about the need for high/low pass filters for listeners who live in the presence of strong broadcasters and interference. Many of the inexpensive SDRs on the market do not have built-in filters and preselectors thus can overload under these conditions.

While filters can be homebrewed or built from kits, these filters seem to be a good deal for a quality shielded and tested product. Thanks for arranging this, Mike!

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CountyComm: Free deluxe case with purchase of GP5/SSB

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Many thanks to SWLing Post contributor, Ron, who shares this deal from CountyComm:

http://www.countycomm.com/gp5ssb.html

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MegaLoop ML052: Bonito’s new portable mag loop antenna

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(Source: Bonito Press Release)

At the beginning of the model year 2016, there is good news in the range of our MegaLoop Active Loop Antennas:

New Model: MegaLoop ML052

The new Active Loop MegaLoop ML052, which is available end of February, is the successor to our MegaLoop 060. Based on the proven technology of theMegaLoop 200 platform, an additional low pass filter with an extra FM-band-stop was integrated. Thus, the ML052 is especially suitable for operation near strong FM-stations and higher frequencies , where, because of its broadband capacity, the ML200 could be overloaded by strong signals.

Frequency range:
Low Gain: 9kHz – 52 MHz
High Gain: 9 kHz – 36 MHz
Suppression on FM (88 – 108 MHz): max. 40 dB

Intercept Point
IP:3: typ. +40dBm
IP2: typ. +84 dBm

The effect of the integrated filter can be seen very good on these two images:

ML052 in High Gain Mode

ML052 in Low Gain Mode

Like the ML 200, the amplification of the ML052 can be changed internally with a jumper:
a) High Gain: 0-36MHz
b) Low Gain: 0-52 MHz (-7dB)
Suppression of the FM band: (88-108MHz): max. 40dB

Outstanding intermodulation surpression, with only 5 volts!

CPI1000 with a standard Powerbank

The MegaLoop ML052 achieved outstanding values regarding intermodulation suppression even at a low supply voltage from only 5V. It can be powered either by a conventional plug power supply or even via USB. Powering via USB has the advantage that no external power supply is needed and that the antenna can be used autonomously and noise-free with a separate USB power bank. A appropriate dual power input adapter (CPI1000) is already included in the standard package.

The MegaLoop ML052 can now be pre-ordered in our eShop underwww.hamradioshop.net. In the UK at Taylor Made RF.

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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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