Differential amplifier and balun/power inserter board, RJ45 to BNC to interface 4 pair cable to coax. 100 ohms to 50 ohms.
This amplifier is designed to be used with a 1 meter loop antenna. It works well from DC to 30MHz. It uses 12 to 14vdc power. The transistors have been matched for performance in each stage to obtain a good differential effect, reducing common mode noise. This combination provides a shielded RJ45 on the balun board to ground the FPA cable shield at the receiver, but the RJ45 is not grounding the shield at the LNA. This is usually the best configuration to reduce common mode currents in the system. The antenna input is diode limited to 0.7v and has VHF/UHF filtering to help protect the amplifier from very strong signals and static noise.
This Differential LNA is providing signals to a websdr using a 1 meter loop antenna like the one advertised elsewhere on this site. You can listen to the websdr to evaluate the amplifier @ http://ka7u.no-ip.org:8074
These boards are custom made by K7RHB and KA7U. You can ask about having specific things concerning these amplifiers and we may be able to adjust the circuits to your needs.
Free shipping within the U.S.A. Please contact for a shipping quote outside of the U.S.A.
This RECEIVE ONLY antenna comes with 100 feet of outdoor rated CAT6 F.P.A. cable, terminated in shielded RJ45 Jacks. A LNA and 2:1 balun with a power inserter, an RJ45 input and a BNC output board is also included. If you need more than 100 feet of cable, add 20 cents a foot for the overage at checkout. Or if you need less cable, deduct 20 cents a foot at checkout.
A user provided BNC cable connects to the Balun/Power Board to your receiver. The supplied FPA cable connects to the Balun/Power Board, and a user supplied 12-14VDC power source connects to the power plug. A demo of this antenna is providing signals to a websdr which can be listened to @ http://ka7u.no-ip.org:8074 .
Shipping is included to the United States. Postage elsewhere will be quoted at time of order.
The antenna is made from RG213/U coax cable, the vertical supports are 1/2″ schedule 40 PVC water pipe, and the box containing the amplifier is a steel outdoor electrical box. Waterproof bulkhead glands are used to seal the coax entry points to the electrical box. A weep hole is drilled in the bottom of the electrical box to allow moisture to escape. The amplifier board is not encased in epoxy and is user accessible.
This is a great antenna for shortwave listening and diversity reception for Ham radio enthusiasts. It works very well with SDR radios and covers from DC through 30MHz. The antenna is broadband and does not require tuning or other adjustment to use.
The antennas are custom made by K7RHB and KA7U, so if you have special requirements, feel free to ask and we might be able to adjust it for you.
Please use the contact form for questions and inquiries.
The Hiletgo LNA and the 1 meter diameter coax loop made such a nice antenna I thought it might be interesting to try another version of an active magnetic loop antenna. So I asked Bob K7RHB to help me to make the Wellgood boards and other parts for the project. We have worked on this together and having lots of fun in the process.
George Smart has parts for one at his website: https://www.george-smart.co.uk/projects/wellgood_loop/ ,and so this is the LNA we decided to build and try out. Unlike the Shielded Magnetic loop made for the unbalanced Hiletgo LNA, this LNA is a balanced amplifier and therefore the loop does not need a center conductor to provide the virtual balun effect to feed the LNA. Just a copper loop is all that is needed to feed this balanced amplifier. We used soft drawn 1″ copper tubing and it is easy enough to form into a loop as it is unrolled from the box it ships in. The CPVC tee is not really strong enough to support the loop in bad weather, so a center support to the top of the loop is a good idea.
After the Wellgood LNA was assembled it seemed to work best with a voltage of 3.1 VDC. The first boards used the 2N3866 transistors and these did not exhibit the gain over voltage increase that we thought they should, so we changed them out with 2N5109 transistors. These transistors seem to operate with better noise floor and gain linearity over a voltage range. We selected 5vdc as the operating voltage for these transistors. A Bias-T printed circuit board is provided with the LNA boards so we soldered up the parts for the Bias-T and made a LM317 voltage regulator from the circuit supplied with the data sheet for that device.
The Bias-T and LM317 board fit nicely in a small cast aluminum box and a 14vdc linear transformer wallwart provides the power to it.
After making the LM317 regulator I learned that http://aliexpress.com practically gives away the LM317 regulators built out for very little cost. You just have to have a month or two to wait for it to arrive.
So does it work better than the Hiletgo Shielded Magnetic Coaxial Loop? Well yes it does, but I’m not sure if that is due to the Wellgood LNA or the larger diameter loop. In order to have a good comparison I need to make a 1″ coax into a 45″ diameter loop and then take comparison readings. I suspect the loop balance with the Wellgood design will provide equal gain end to end and good nulls side to side, while the Shielded Magnetic Loop may not exhibit that excellent balance. Still, objective testing has not yet been done here to really know.
An affordable do it yourself active loop antenna that covers 15KHz to 32MHz and probably more, is roughly represented by the following sketch.
To further describe this antenna shown in the sketch, it is 1 meter in diameter more or less, and the coax could be any coax that is available. I used a foam filled RG8 which is very flexible and doesn’t hold a shape. LM400 or other solid dielectric coax should be a better choice. I was experimenting on this build and I’ll choose better material on my next build.The Hiletgo LNA is an unbalanced amplifier that works from 100KHz to 2GHz according to the spec. I find it works from 15KHz to probably 2GHz…, but in my case to 32MHz for sure. At the time of this writing this amp is available at Amazon.com, search for: HiLetgo 0.1-2000MHz RF Wide Band Amplifier 30dB High Gain Low Noise LNA Amplifier I paid $10.99 for it delivered with Amazon Prime.
This Hiletgo LNA works with power up to 12vdc but I found that it only takes the 8 vdc to work down to 15KHz effectively. The DC power needs to be clean DC and the voltage should not exceed 12VDC or you may experience noise issues with the little amp. I used power over the coax to power it and so I needed to add a 1mh inductor from the coax center conductor to the +vdc input on the board. This being placed on the line side of the little input capacitor already inline on the board effectively isolates the input power from the LNA input. See the following image.
Aliexpress.com is currently selling a low cost Bias-T that works down to 1MHz. I suspect it will be fine to use with the Hiletgo LNA. Search for Tee Bias on the website. There is also a 9vdc clip soldered to the power input, but that was just a temporary testing solution. You might notice the Hiletgo LNA has SMA connectors in and out and I chose to use those to make connections to it with coax pigtails and adapters for testing. These could be removed if the board was to be installed permanently in a box and then connections soldered. I will probably continue to use adapters for ease of changing the amplifier even if I put it in a box or pipe.
The following image shows the current connections to the antenna and LNA.
This antenna is currently connected to a KiwiSDR at http://ka7u.no-ip.org:8073 . It won’t stay there long as a new one will likely be installed soon.
And sure enough, here is the updated version of the loop antenna. The 1/2″ PVC pipe is not glued and is depending on compression and friction to stay together. This makes it easy to take apart and use portable.
So here is an image of the waterfall shown side by side with a waterfall image of a 210′ dipole for comparison.
It occurred to me to check the relative antenna / LNA. I connected a 50 ohm load to the transmitter and set it for 5 watt carrier output. Transmitter is 100′ from the loop antenna. The loop and Hiletgo amp provided these results into the KiwiSDR.
28.5MHz – -69dBm
24.9MHz – -63dBm
21.2MHz – -48dBm
18.1MHz – -44dBm
14.2MHz – -54dBm
10.12MHz – -53dBm
7.15MHz – -57dBm
5.33MHz – -59dBm
3.75MHz – -67dBm
1.9MHz – -90dBm
The antenna impedance measures low < 50ohms on 21.2 and 18.1MHz. This would make me think the Hiletgo does better with a low antenna impedance.This antenna is dropping dramatically at 1.9MHz which is the lowest transmitted signal used. The antenna does receive the MF broadcast band quite well and so it might be a spot in the system that attenuates more than others or lower radiated power from the 50ohm load resistor and cables.
Inspiration for experimenting and building this loop is taken from the following web sites:
Video discussing setting the Hiletgo LNA for best SNR. If you don’t want to watch the video, use 8 to 9vdc and you should be fine. 8vdc seems to give the lowest noise floor and 8.5vdc might be just a bit better on SNR.
After John Seamons added a 10KHz IQ stream to the KiwiSDR clients, the opportunity to send the SDR IQ data to another receiver such as HDSDR or Dream DRM receiver needed to be setup! There are general instructions at kiwisdr.com located here: http://kiwisdr.com/quickstart/index.html#id-faq-drm
The system I chose to configure for this service sports an Intel I5 2nd generation processor and 8Gb of RAM. So not a super duper computer, but a serviceable one. It is using openSUSE 42.3 for the operating system and the standard and community repositories are installed, including this one: http://download.opensuse.org/repositories/hamradio/openSUSE_Leap_42.3/
The Dream receiver is available in the above repository as well as the codec that is needed to decode the DRM signals.
faad2, libfaad-devel, libfaad2, libfaad_drm2, are all installed on this system.
Pulseaudio, Alsa, and Pavucontrol are installed. Google Chrome and Firefox are the web browsers in use.
Pulseaudio is configured to provide a virtual audio cable with the following command sent via the terminal: ron@linux-4cdz:~/> pactl load-module module-null-sink sink_name=MySink \ sink_properties=device.description=”MySink” 25 ron@linux-4cdz:~/
To make the audio connections, open a KiwiSDR client instance in your web browser, such as http://fenu-radio.ddns.net:8073/?f=3965iqz8 , then start Pavucontrol. Open the “Playback” tab and select “My Sink” for the output of the Web Browser. Start Dream then in the Pavucontrol “Playback” tab select “Built-in Audio Analog Stereo”, or whatever your normal sound card is, as the output for the Dream receiver. In Pavucontrol open the “Recording” tab and select “monitor of My Sink” for the input to the Dream receiver.
In the Dream receiver open Settings/Sound Card/Signal Input/Device and select ALSA:Pulse, then open Settings/Sound Card/Audio Output/Device and select ALSA:Pulse.
In the Dream receiver open Settings/Sound Card/Signal Input/Channel and select I/Q Pos Split.
All things being operational, you should hear the DRM station audio. If a DRM station is not available, you can use the Dream receiver to listen to other modes, just pick one and listen to it.
This video might be more understandable then my notes:
Using the RTL-SDR units and OpenWebRX the bandwidth was limited to 3.2Mhz or less and the waterfall seemed to have resolution limitations. The receiver controls were limited by comparison to the KiwiSDR control, and the frequency stability of the various RTL-SDR units was not uniform from one RTL-SDR to another. So when I was able to buy a shiny new KiwiSDR with the promise of a better receiver with more control, I ordered it in!
The KiwiSDR requires a 5vdc supply. I bought one of the suggested supplies listed at the KiwiSDR quick start site, and as the KiwiSDR arrived before the power supply, I was able to learn something. The KiwiSDR cape board draws more power than a normal BeagleBone can provide, but the cape is capable of powering the BeagleBone and the Cape. So powering through the mini-usb port in the normal way is not possible. The barrel connector power supply connected to the Cape is the only way to go. Once I got the power supply all was well. You can of course remove the Cape and power the BeagleBone in the usual way for loading the software and other tests without the KiwiSDR attached. I also learned that when installing the software it is best to remove the KiwiSDR Cape, as it is easier to install the Micro-SD card. Once the card is installed, power the BeagelBone on using the standard mini-USB type power supply, watch the LED blink for about 4 minutes, and when the BeagleBone shuts off, remove the mini-SD card, reinstall KiwiSDR Cape, use the barrel connector power supply with the Cape, and remove the mini-USB type power supply from the BeagleBone if it is still attached. The KiwiSDR is now up and running.
I had some frustration getting started with the KiwiSDR admin page. I was editing the information in the fields of the web browser without difficulty, but when it was time to restart the KiwiSDR to save the changes, I could NOT see the unit restarting. I learned that there is about a 30 second delay from the time you click on the restart button until it does restart. The Title field on the admin page has a lot of html and it was not quickly apparent to me that I needed to edit the Title field, duh… Anyway, I did connect to the KiwiSDR via SSH, poked around a bit in the root directory, and using vi edited the kiwi.json file to change to my call sign. So I had the “new user” errors, but overcame them. I did find that if the KiwiSDR is running on the web browser when the admin restarts are done, it is easy to see that it restarts! I wrote to John, ZL/KF6VO and told him about my initial challenges, and he did not stop writing to me until he was satisfied that I knew what needed to be done and to verify that his code was working correctly on the web browser, which it was. I must say I believe John will try all he can to make sure you do not fail if you are setting up a KiwiSDR. A++++ for service in that regard!
Using the KiwiSDR is a pleasure. The GPS unit keeps the KiwiSDR on frequency and stable. Decoding digital audio modes has been flawless using Fldigi with Pulse Audio. There are some nuances to using the radio controls of KiwiSDR on the web browser waterfall.
First thing to do is explore all the control buttons and understand what each one does. There are pop up menus that appear when you hover the mouse over the menu button. The “More” button takes you to the AGC controls.
Generally for SSB I’ve found settings of 100 for Threshold, 3 for slope, and 1000 for decay, yield good results. CW probably works best with 130 for Threshold, 1 for slope, and 350 for decay. Tuning with the mouse has a some options. SSB with a left mouse click centers the bandwidth over the click, whereas a “shift-left click” places the bandwidth beginning at the “shift-click”, which is usually the best way to tune with a mouse on a SSB signal. The left mouse click is excellent for tuning CW however. There are probably more tuning options, but those are the ones I’ve found, well there is also the “shift-left click and hold”while dragging the bandpass tuning around…
Currently, I’m using a 210 foot top G5RV up 38 feet for an antenna.
This antenna provides to much voltage on the AM Broadcast band and overwhelms the KiwiSDR, so I’ve placed a MFJ-1046 Passive band-pass tuner in the antenna line, and it is usually set for the 6.4-11.5MHz setting. This seems to attenuate the AM Broadcast well enough and yet pass most all signals reasonably to 15MHz. Frequencies higher than 15MHz are more severely attenuated. I would make a high pass filter beginning at 2MHz for this purpose, but I have ordered an active mini-whip antenna made by RA0SMS and it is my hope that it will be an adequate antenna across the 30MHz band without need for additional filtering.
Nov. 23,2016. Time for an update.
The KiwiSDR is still using the above antenna. I had some trouble with the mini-whip and a
new one has not yet arrived. The MFJ-1046 cut off to many frequencies, so after considering
the problem, KKOO @1380KHz seemed to be the power station creating images and noise. A series
resonant LC circuit is now in the antenna line effectively attenuating 1380KHz by over 20dB
and the problem is solved.
The circuit is made of 4000pF mica-capacitors, and 26 turns of 24ga wire on a T50-2 Toroid
core. One side of the circuit to the antenna input, and the other end to ground. See the
images to visualize the effect of this little wave trap on the receiver performance.
Locally, the Hams are using it for a diversity receiver and it is helping some people to hear better when the noise levels are overwhelming in the more urban settings. Some are using it for shortwave listening. It is new here, but I think this KiwiSDR will get a lot of use over time.
There are other developers working to bundle hardware and software to use Mr. Retzler’s OpenWebRX engine. An example of this is found @ http://www.jks.com/KiwiSDR/ . So consumer grade products are on the horizon for this application. But being a Ham, I’m more interested in “rolling my own” to the extent practical.
The advantage in use is lower throughput required to monitor a section of spectrum, but it comes at the expense of higher resolution that I’ve come to expect with the USB connected RTL-SDR, and the Network connected RTL-TCP server. So listening to the radio on a web browser is a good tool, it does not replace the higher resolution and spectrum views provided by SDR# or HDSDR. I imagine I could monitor my transmissions at various locations around the world by opening an OpenWebRX station at that geographic location and monitoring my transmitted frequency. DX all by myself, well nearly. LOL
In rpt.conf there are stanzas that start with the node number, such as:
 ; Change this to your assigned node numberrxchannel=Radio/usb;rxchannel=Simpleusb/usbduplex=0~archivedir=/media/USB
If it contains the “archivedir=<some recording location>” as shown above, then the audio passing through the radio will be recorded. In my case the recording location is a USB stick formatted as an ext4 file system identified by the system as /dev/sda1. So edit the file /etc/fstab and add a line as shown in bold below:
The AllStarLink system will add the node number to the directory structure, so when you navigate to the saved audio files, you will do something like this:
[root@AllStar-KA7U /]# cd /media/USB/28174[root@AllStar-KA7U 28174]# ls -ltotal 1188-rw------- 1 root root 6154 Mar 15 21:22 20160315.txt-rw------- 1 root root 12800 Mar 15 20:51 20160315205145.WAV-rw------- 1 root root 5455 Mar 15 20:51 20160315205153.WAV-rw------- 1 root root 5130 Mar 15 20:52 20160315205159.WAV.... snip...
As you can see above the system has been busy recording audio files in the mounted USB stick. To use these files, we need to copy them to a computer capable of playing them. In this case the Raspberry PI is connected to another Linux computer by SSH, so we will copy the desired files to the connected computer with the SCP command issued from the connecting computer in the directory we wish the files to be copied to. Note: there is a space between *.WAV and ./ , don’t forget the space. 🙂
From here we can play the files one by one in a player of choice, such as Audacity, or we can concatenate them into one or more files using SOX. Without our intervention, SOX will concatenate the files in the correct date and time order with the simplest command.
ron@linux-zdyj:~/wave> sox *.WAV test.wavron@linux-zdyj:~/wave> ls -l test.wav-rw-r--r-- 1 ron users 1034926 Mar 15 21:42 test.wavron@linux-zdyj:~/wave>
Notice in the above that a new file “test.wav” now exists. Also note that the AllStarlink system uses a naming convention on the audio files using capital letters WAV. Audacity has the ability to further edit the file and change from wav to other codecs such as mpg. This screenshot shows the presentation of this audio file in Audacity.
The file is linked above, if you would like to listen to it or work with it. This recording is quite useful in as much as one of the radios has an intermittent connection problem and one of the radios is over modulated. The picture in Audacity is worth a thousand words, and being able to listen to the audio more than once, makes it much easier to determine how things sound.
If the radio is breaking squelch to often, the recordings of that will be plentiful. So if we plan to record, the squelch should be sufficient to silence the radio until a signal appears.
This is a copy of the relevant post. If you have relevant information, please leave a comment about it.
The R-1200AX is the basic 1200 with the option of a high stability timebase (the "X.")
The modules have been added later.
There is no internal load in this model. It is designed to monitor off-the-air signals or
to be used with a pick-off enroute to an external dummy load or antenna.
I don't have the manual anymore, but this is how it works to measure deviation and frequency:
1) Dial up the known carrier frequency
2) Press the RECEIVE button
3) Press 1.5, 5 or 15 KHz to select range (FREQ ERROR)
4) Connect whip antenna or cable from pick-off to broadband mixer
5) Place wide/narrow switch in "wide" unless there's interference, in which case use "narrow."
6) Read frequency error on ERROR KHZ meter
7) Set deviation meter range as desired
8 ) Read deviation on meter when transmitter is being modulated
Unfortunately these are 30+ year old instruments which have usually seen a hard life.
They are worth little on today's market, as they have no value to commercial shops, thus
intensive labor to get one running has to be considered a lost cause at some point.
I have had some where the electrolytics in the deviation meter module were totally dried out
and open circuit. Other electrolytics in the unit, same story. Tantalum dip capacitors can
be shorted, they are becoming notorious for this.
The manual, as I recall, is rather huge and would be a life's work for someone to scan
and put on the internet. Operating the thing should be a pretty intuitive process.
For generating a signal, use the CW position generally as that is locked to the TCXO.
The red "Leveled" lamp should be lit normally. If it is out, it means the output has
either become unstable or the overload protect circuit has tripped (hence the reset button.)
The FM Cal knob sets the frequency when the generator is in the modulated FM mode.
It should be zeroed with the zero center meter. The stability while in the FM modulated mode
is rather poor, it's just for testing receivers and not frequency setting. Leave it in
posted by: Geoff Fors
OK, so after reading the above I setup to test the Service Monitor on the bench. I decided to use it in FM modulated mode to see how unstable that might be too. This video pretty much tells the story of how that worked out. https://www.youtube.com/watch?v=a5lSJb3t4nc
DECT telephones offer advantages for wireless because they use different frequencies than WiFi. I have 3 telephones registered with the base unit and the base unit is registered with an Asterisk ver.13 PBX as SIP extension 7005 using voicemail box 8005. (This means that when the extension is called, all 3 telephones ring. The phones can be configured to ring individually on different extensions. That is up to the user.) This DECT set is working with the Asterisk ver.13 configurations found in my previous post, title: Configuration Files for Asterisk v.13 and AllStar Link . The network it is configured for is a HSMM-Mesh Network, so if it were to be configured for a normal LAN the host names would change to IP addresses.
Quick Start: A newly purchased KX-TGP500 base unit that is “open” (that is not pre-configured by a provider) and a KX-TPA50 handset need to be powered on. The handset needs to be registered with the base. To register the phone with the base you need to do the following:
Open the menu of the handset by pressing down on the joystick on the telephone
Then press #130 on the telephone dial pad
There is a button located on the DECT base unit. Press it down for 4 seconds
Then press OK on the Telephone, which will be the button to the right of the word menu just under the screen.
Then dial 0000 on the telephone. Once it returns to the normal screen the handset should be registered and show you a number beside the battery symbol in the screen.
This needs to be done for each phone being registered.
To open the HTML configuration for the base unit, you need to press the joystick on the telephone down and then select the “tool box”, “Network Settings”, “Embedded Web”, and then “On”. The phone will sound a long tone. Then from a web browser sharing the same LAN, type in the IP address of the DECT base unit. You can find this IP address on the telephone by pressing down on the joystick and selecting the tool box icon, then Network Settings, then IP settings. Log into the DECT Base unit HTML configuration with the default username Admin and default password adminpass. Select the VoIP tab on the top menu, and then “line 1” under “SIP Menu” from the left sidebar menu. You should now be on a page that looks like this image:
You may want to change the addresses from ka7u-2 to your host name or IP address and the extension number is the authentication ID in my Asterisk PBX. The authentication password is the “secret” for the extension as listed in sip.conf.
This should be enough configuration for the DECT phone system to work with Asterisk ver. 13 PBX. There are many other configurations according to your needs.