All Questions

Filter by
Sorted by
Tagged with
0
votes
1answer
31 views

Estimating SWR based on multiples of resonant length

I am planning to buy a Xiegu G90. It has an internal tuner that can tune up to SWR 5:1. Does anyone know if I have a resonant antenna on 40m, what I will have for a SWR on 80m?
0
votes
1answer
47 views

Circuit for RF Splitter [closed]

Does anyone know of any resources which describe how to design a circuit with one RF input and multiple (at least 6) RF outputs, whereby the signal strength of each output matches (does not exceed and ...
0
votes
1answer
16 views

4NEC2 shortening factor “x”

I read on pg5 of Antenna Simulation with 4NEC2 about shortening factor "x". It is very specific and I can't figure out how to use it in a general nec file. It sounds like SY x=0.907 in the ...
3
votes
5answers
191 views

How does IQ modulation work (intuitively)?

I'm trying to get my head around IQ modulation. What I understand so far is that each of the I and Q branches of the mixer produce two sidebands with the same frequency components, but in the Q branch,...
1
vote
1answer
19 views

How to model a curved element in 4NEC2

I am in kindergarten with 4NEC2 and trying to model a Gray-Hoverman TV antenna. I have someone else's model and understand most of the file parameters. I have added VHF elements that have S curves at ...
1
vote
0answers
24 views

Installing GNU radio on android

I want to install this miracle program on my smartphone in order to get more mobility. I found such a solution exists: https://github.com/bastibl/gnuradio-android However, I could not do everything as ...
3
votes
3answers
65 views

If a sealed, non-airtight pipe is used as antenna element, how big of a problem is condensate trapped inside?

I'm building a vertical antenna. The lowest portion of its element consists of 3/4" type M copper pipe, with end caps that will be soldered on and 3/8-24 screws poking through at both ends (so ...
1
vote
0answers
15 views

#APRS error ? (only visible on aprsc status)

I'm playing with Nodered that I'm trying to use to place an aprs object: it works but it does not suit me! No error on findu.com, correct display of frames on aprs.fi or on aprsdirect.com ... but on ...
1
vote
1answer
48 views

Does the FCC e-mail when a vanity call sign is approved?

I submitted an application for a vanity call sign a little over 18 days ago, and it's marked "pending". I presume that it will be processed soon, but the FCC's ULS search page is being slow ...
0
votes
1answer
41 views

Lowest noise MMIC for HF? (160-20M)

I recently learned that these fancy modern ultra-low noise MMIC, while having <1dB noise figure around 1Ghz could be quite bad at low frequencies due to 1/f noise. What is lowest noise MMIC then ...
2
votes
3answers
74 views

How is the Hackrf able to achieve 20MHz of bandwidth with an ADC that only allows 22Msps?

The way I understand it, is that to avoid aliasing on an ADC, you have to be in the first Nyquist zone (so half the sampling speed). What doesn't make sense to me is how the Hackrf is able to bypass ...
0
votes
1answer
25 views

Software to model autotransformer matched end fed dual band, 4nec2?

I have several ground independent dual band antenna of different makes, but they all have the same type of matching circuit to make them ground independent / radial-less and match say 5/8 elements, ...
0
votes
0answers
18 views

Setting the maximum Tx Power value for the USRP transmitter

In order to simulate the measurements on the computer (in the WinProp environment) I have to set the maximum Tx power: To find out what the transmitter signal power is, I checked it on the spectrum ...
4
votes
1answer
86 views

Frequency selective surfaces working principle

I've seen that sometimes frequency selective surfaces are used to load a certain impedance to a certain antenna (for instance for input matching purposes). These surfaces act like a filter on the ...
-2
votes
0answers
31 views

Just wondering if the following is possible [closed]

I'm sorry to bother but I have some questions and feel so lost reading some answers it's a foreign language so I was wondering for what reason would there be a ton of wires all going into my seat in ...
4
votes
2answers
187 views

What do you call antenna that combines multiple Hustler resonators (using a VP-1) above a shared mast?

I know that a Hustler MO-3 54" mast with something like a RM-20S resonator on top is officially an example of a center-loaded quarter-wave vertical... ... but Hustler also allows you to mount ...
0
votes
0answers
21 views

Viewing SSTV with QSSTV/GQRX

I have an IQ file and have the following information: 7.171Mhz / 2.5 megasamples per second My question is with this information, can I view view from the IQ file ...
1
vote
2answers
120 views

How many cars/devices can connect to a transmission from a 7 Watt FM transmitter

I currently own a 7 Watt Frequency Modulation (FM) transmitter that I purchased from eBay some years ago. We are planning a drive-in cinema setup where the transmitter will be placed 5 meters above ...
2
votes
1answer
64 views

Why is QRN so bad on the low HF and MF bands?

If one tunes an HF/MF radio at night, the lower the frequency (or the longer the wavelength) of the band, the more QRN (static and atmospheric noise) there is. 80m is noisier than 40m, and 160m is ...
0
votes
0answers
23 views

Can I use a DireWolf based digipeater to work the ISS digipeater?

I've recently become interested in ham radio, particularly AX.25/FX.25 packet radio. I ordered the basic setup (RPI, DireWolf, BaoFeng, a sound card, and some cables) and I was wondering with this ...
2
votes
2answers
86 views

Selecting antenna for rocket telemetry system

I'm currently in a rocket team and we are building a rocket that can reach 3000m (10.000 feet). I am responsible to find an antenna for the telemetry system. I was searching on the net to find the ...
0
votes
1answer
14 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
59 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
54 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
86 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
59 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. ...
0
votes
0answers
36 views

Charly 25 vs mid/top-end SDR transcievers

I am interested in independent theoretical performance feedback for Charly 25 SDR (based on RedPitaya 122-16 board) compared to more conventional SDR transceivers like ICOM 7610: Reference clock ...
3
votes
2answers
143 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
57 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 (...
8
votes
2answers
594 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
48 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
78 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
44 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
94 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
85 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
236 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 ...
2
votes
1answer
24 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
118 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
70 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
101 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?
4
votes
3answers
620 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
88 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 ...
0
votes
0answers
6 views

How to choose a substitution transistor for a feedback amplifier? [migrated]

I'm experimenting with RF feedback amplifiers (this topic is well covered in "Experimental Methods in RF Design" book, if anyone would like to know what that is). Particularly I'm interested ...
1
vote
4answers
228 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
44 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
29 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
4answers
130 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
74 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
44 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. ...

15 30 50 per page
1
2 3 4 5
74