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1answer
22 views

Connecting Mobilinkd TNC2 to Mac for Xastir

I am not sure what to put in the TNC Port window on Xastir if I'm using a Mobilinkd TNC2. Xastir has directions for just this however, it is for Ubuntu Linux. https://xastir.org/index.php/HowTo:...
2
votes
1answer
67 views

Reducing cross-band noise from plasma TV

I have a noise problem on 40, 20, and 15 meters originating from the plasma TV I own. Turning on the TV raises the noise level by 2–4 S units, depending on the frequency. The TV is located below the ...
3
votes
1answer
65 views

How do I write a modem for DireWolf?

I was looking at the selection of modem bauds for DireWolf and it seems the highest baud modem is 9600 baud, and I am using a sound card that can reach 48 khz. Is there any way that I can write a ...
2
votes
2answers
110 views

Coupling 2 Antennas to one line?

Imagine two dipole (or Yagi) antennas as might be used to create a circularly polarized combination antenna. The two are physically oriented (rotated) by 90 deg, and if in the same receiving plane, ...
5
votes
1answer
70 views

can the adhesive used in thru-glass antenna couplers be replaced?

I recently bought a pair of self-adhesive thru-glass antenna couplers for my mobile radios and erred in mounting both of them, which required me to peel them off the side window glass in my minivan. ...
3
votes
2answers
170 views

Dual Polarization Yagi Antenna for 10 m

Imagine that someone has built a 4 element horizontal yagi antenna for 28 MHz with elements insulated from the boom, and with the driven element not split in the middle and using a gamma match to set ...
1
vote
2answers
228 views

Yaesu FT-70DR Earpiece

I recently purchased a Yaesu FT-70DR and would like to use an earphone of some sort just to listen. On Yaesu's site, there seem to be only 2 official options: SSM-57A Earbud speaker mic with PTT (...
9
votes
2answers
689 views

What is the appropriate length of an antenna for a handheld on 2 meters?

I want to upgrade the stock antenna on my Baofeng uv-5r for which I mostly use the 2 meter band. The quarter wavelength for this band is about 19.2 inches, but when I look for antennas, they are ...
3
votes
0answers
62 views

Any tool for finding satellite passes that overlap *two* given locations?

gpredict is nice. Well, it's OK, to find the next passes for a set of satellites with sufficient elevation for one location. What I want is something where I can put in two coordinates, and get out ...
0
votes
0answers
28 views

USA made handheld [duplicate]

I am looking for advice on new to HAM studies. I have a pair of FRS Motorola T800 walkie talkies and an old pair of REalistic TRC-215 6 channel, 5W, CB handhelds. As I read, and ask questions, a ...
4
votes
1answer
162 views

Debugging SM0VPO's spiral loop antenna build

I had built SM0VPO's spiral loop antenna. And here it is. Recently I got myself a NanoVNA to see how finnicky it is to be tuned with that poor man's tuning cap. I brought it from 12 MHz into the 14 ...
2
votes
0answers
56 views

Biconical antennas - bandwidth and installation

I am posting this question (and its related question) here because of the unique expertise that Ham Radio Operators have as it relates to antennas. I'm a newish Ham and really appreciate your help ...
1
vote
2answers
167 views

Trying to identify and understand this antenna design - ground independent dual band vertical

This is the insides of a common dual band antenna 2m/70cm, made by diamond or nagoya. its generally labelled as: 1/2 wave radialless (144MHz), 2 x 5/8 wave radialless (430MHz) Its meant to be ground ...
2
votes
3answers
104 views

Constructing a ground level antenna array to monitor radio frequencies using SDR

New to this community and also a newish Ham. Hello everyone. This question could easily have been posted under 'Astronomy', but I thought I would start here since Hams tend to be quite knowledgeable ...
3
votes
3answers
276 views

Is The Lowest Antenna Terminal Feedpoint SWR Always Optimal?

Intuition might lead one to believe that the antenna configuration with the lowest SWR(50) across its input terminals would provide the best radiation efficiency for the antenna system. But is that ...
3
votes
1answer
27 views

alinco dr-635T receive squelch will not open in DCS mode

Newbie here with a question: I have programmed my Alinco DR-635T for use with a variety of local repeaters. Half of these are opened with CTCSS codes and the rest with DCS codes. When monitoring any ...
5
votes
2answers
170 views

Can an oscilloscope be used as an RF voltmeter?

I just recently acquired a slightly functional Icom IC-735 HF radio, and am trying to resurrect it. The service manual outlines procedures that specify the use of an RF Voltmeter, which I do not own. ...
4
votes
3answers
99 views

High-Z RF amplifier for magloop RX vs Q-factor

I've noticed that increasing load on magloop reduces it's Q-factor, it becomes less selective. Traditional way to approach this is reducing size of pickup loop, or alternatively, using transformer. ...
-4
votes
1answer
107 views

Power, Tower, and connection [closed]

Ok so lets say we have communications tower number 1 and comms tower number 2, if one were to get wiped out by a power surge, could the other sustain connection to the area?
5
votes
3answers
644 views

Can SDR receivers be detected remotely?

It's my understanding that active superhet receivers can be detected by looking for the emissions from the local oscillator, particularly because the LO's frequency is usually set at some fixed offset ...
4
votes
3answers
96 views

antenna coax feed-thru for a car roof

Newbie here, with a 2 meter mobile rig and a magnet-mount antenna. I am currently routing the coax out an almost-closed window and am tired of having rain water enter the car through it. Is there such ...
1
vote
4answers
261 views

Will the feds show up to my door? Is there a way to not get in trouble?

Ok so I am in the USA, and I have just bought a BFTECH BF-F5XP. I have a couple of questions. First of all, could I make my own Privacy code (Interference prevention code), and channels? What I am ...
0
votes
2answers
86 views

cant get my bftech radio to program with chirp software

I have a bftech bf-f8rt and they dont show that radio on chirp will they update chirp for that radio? Is there another place like chirp to program it or do i have to do it manual
0
votes
0answers
30 views

16-FSK recovering bits

I'm looking for help with one exercise. Firstly I was supposed to download modulated signal. (It's Olivia 16-FSK) [y,fs] = audioread('Olivia16-500.wav'); And then ...
4
votes
5answers
315 views

Is spacing of fan dipoles necessary?

Is spacing of parallel dipoles necessary. Could they be banded together and then trimmed or is there some consideration, other than tuning, requiring separation. I was considering a fan dipole. I ...
2
votes
3answers
87 views

what is the baseband for CATV?

I was reading on wikipedia this: the subscriber's television or a set-top box provided by the cable company translates the desired channel back to its original frequency (baseband) But when I ...
1
vote
2answers
87 views

Alinco DR-635 programming software

I see that RT-Systems sells programming software and a cable so you can program the Alinco DR-635's internal memory via your laptop instead of through the Alinco's cryptic and hostile user interface. ...
3
votes
2answers
119 views

Why am I receiving a local tv channel on a CMB frequency

I am using a simple Baofeng H6 dual band radio and I programmed weather channels. Well, on frequency 161.77500 I am actually picking up WGN, a local tv network. This frequency should be reserved to ...
0
votes
0answers
55 views

RS41 weather balloon unable to decode data

Some times ago I tried to decode the signal from a weather radiosonde (RS41) passing in my area using a cheap RTL SDR (using both standard antenna and a home-made one, with similar result). The ...
0
votes
1answer
62 views

I have a 433MHz LoRa Dipole antenna mounted on a rocket. I am looking for a suitable Antenna to receive data from this. Any Suggestions?

The idea was to send GPS data from the rocket to the ground station at 433 MHz using a Lo Ra transmitter - mainly to help locate it once it lands and also to provide in-flight telemetry. I have a ...
0
votes
0answers
69 views

gnu-radio on Ubuntu 20.04 and AIS processing seems impossible

I have searched, installed, and tried every package there is to get AIS processing using the gnu-radio companion to no avail. I tried installing gnu-radio both with conda and apt on Ubuntu 20.04. The ...
6
votes
6answers
237 views

If receive performance doesn't depend on SWR, then how can I tune my manual HF antenna tuner by band noise?

The popular question "What is the relationship between SWR and receive performance?" asks if a receiver with a well-matched antenna (low SWR) beats a receiver with a poorly-matched antenna, ...
1
vote
1answer
63 views

Will Brexit have any impact on UK recognition of foreign licenses

As a US license holder (and duel citizen of the US and UK) I know that I can operate in the UK for a couple of months using the M/W2*** prefix, while holding Amateur Extra, but I cannot apply for a UK ...
1
vote
1answer
81 views

Anytone 878 UV Commercial license?

This radio has a commercial mode but no where that I can find does it describe which commercial license. Looking at the tag under the battery... FCC ID T4KD887UV https://fccid.io/T4KD878UV ...so part ...
3
votes
1answer
158 views

What do old unit abbreviations like “mfd” and “kc” mean, and where did they come from?

I saw a recent answer that mentioned "mfd" as a unit of capacitance, and I can recall having seen that term in old schematics and ham radio articles. I've also seen other non-SI unit ...
3
votes
3answers
101 views

What causes an AF amplifier to make popping sounds in a superheterodyne receiver?

Recently I've made a simple single IF superheterodyne SSB receiver for 40 meter band. The schematic is available here [PDF]. VFO and BFO are based on Si5351, the AF amplifier is LM386. It works OK but ...
9
votes
2answers
3k views

Am I really receiving FT8 signals from 12,000 km away on 144 MHz?

I have been using an Ettus B200 SDR to receive FT8 transmissions in the 2-meter band (144.174 MHz) using the WSJT-X software. Signals are received using a telescopic antenna inside on a window ledge ...
5
votes
2answers
659 views

What does ALC do on a transceiver?

What is ALC on an HF transceiver? What are the disadvantages (if any) of operating using a rig without ALC? What might be the difference between a good and bad implementation of ALC?
5
votes
2answers
97 views

How is phone cable with iron called?

In in Russia I saw a phone cable called "field cable" (провод полевой П-274-М). It is a loosely twisted pair with some iron strains added alongside with copper ones. I tried to lookup ...
2
votes
1answer
58 views

Identical HF Horizonal Dipoles Operating in Close Proximity

I'm planning to use a multiwave horizontal dipole oriented to work comms toward Alaska from Colorado. That ends up being awkwardly oriented to work east coast and Europe. If I placed a second ...
3
votes
1answer
77 views

Modeling a regenerative receiver

What is the signal processing model of a simple regenerative or super-regenerative receiver? Is it just a linear 2-pole IIR filter with gain? How does a single regen control knob control both ...
1
vote
1answer
45 views

Excitation coefficient of a linear phased array

it's well known that in a linear and equispaced antenna array, the array factor is equal to: The array is then called uniform if $|I_n| = I$ is the same for all elements. The phase terms $\angle I_n$ ...
4
votes
3answers
218 views

Is an antenna always matched to free space impedance?

In this thesis the following model for an antenna is proposed: It is seen as a 2 port network, in which only port 1 is accessible (port 2 is an imaginary connection between the antenna and the free ...
4
votes
2answers
223 views

If repeaters share the same call sign are they “Connected”

Newbe here, I was looking through repeaters in my area and I noticed that there were a few repeaters that shared the same call sign(even though they run on different frequencies). Does this mean that ...
0
votes
1answer
77 views

Sweep times for Spectrum Analyzer

I have a basic question about sweep times and number of points. My frequency span of interest is: $f_{span} = 30\ \rm MHz$ My resolution bandwidth is: $RBW = 10\ \rm kHz$ The minimum number of points ...
1
vote
1answer
38 views

How to avoid acoustic feedback while fixing radios?

CQ CQ CQ de BH4FHO. I have been fixing some radios recently - buying used radios for cheap, fix them up and modify them to transmit in ham bands. When testing them out, I am using my Baofeng DM-1801 ...
0
votes
1answer
72 views

Troubleshooting the MFJ 1982 EFHW

I am a beginner with not much experience in HF. My shack consists of a Xiegu G90 connected with 20ft of RG-8x to an MFJ 1982 end fed half wave antenna. There is a small coil of coax next to the ...
2
votes
2answers
120 views

Is it at all possible to make a ham alert radio?

Would it be possible to make an alert radio... for shortwave? Out of something like Arduino, or RPi. Sort of like the NOAA Weather Radios. I got to thinking one day. Say you wanted to send a message ...
3
votes
1answer
144 views

Looking for origins of a crystal filter schematic used in uBITX

Here is a crystal filter used in uBITX transceiver: I've never seen such a topology in any other transceiver and decided to invest some time in exploring it. Turned out it's quite interesting. Eight ...
1
vote
1answer
92 views

Obtaining input/out impedance from S-parameters for a L network

This L network intend to transform Z1 to 50ohms. The design was made using a smith chart: The s-parameters plotted (S11 red - S22 green) in the smith chart is done sweeping the frequency from 200MHz ...

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