Questions tagged [uhf]
Ultra High Frequency is the frequency range 300-3000 MHz.
89
questions
2
votes
1answer
50 views
Help understanding transmission loss of trivial circuit
I was trying to DIY a VHF/UHF diplexer, and got some weird readings from the VNA.
By debugging I reached this trivial circuit:
Which has the following frequency response:
I'm trying to figure out ...
4
votes
1answer
115 views
Does a UHF/VHF handheld transceiver kit exist?
I am a licensed ham looking for a UHF/VHF handheld transceiver kit. Unfortunately so far I was only able to find broken links, i.e. Ten-Tec used to produce exactly such a thing but they just don't ...
1
vote
3answers
545 views
Why aren’t emergency services using callsigns?
I’m super new to radio with nobody I know knowing it, so noob alert - plus some extraneous details in case you can comment on any of those.
I got a pair of BaoFeng BF-F8HP radios with recommended ...
2
votes
3answers
723 views
VHF 50 Ω Antenna Over 75 Ω TV Coax
I have a 50 Ω VHF airband antenna which I’m planning to install in my loft, for use with a RaspberryPi-based RTLSDR scanner/receiver.
I already have a UK-standard UHF/Freeview antenna using standard ...
1
vote
1answer
79 views
Simple antenna for LoRa 433 MHz module
I have some LoRa SX1278 433 MHz modules:
However, I don't have an antenna. My question is: what would be a good antenna option for longest range? I don't really care that much about transfer speed, ...
5
votes
2answers
118 views
Is there any practical advantage to a parabolic reflector over a high-gain beam antenna?
I've been looking at options for a high-gain directional antenna recently, and I've noted that there are commercially available parabolic antennae for the shorter bands -- specifically 70 cm, with an ...
2
votes
2answers
117 views
Bad squelch on a TYT MD-380: user error or hardware?
I have a new TYT MD-380; it works well for DMR channels, but on analog, the squelch doesn't seem to open when it should. I'm relatively new to ham and my first suspicion is user error, but it's ...
2
votes
3answers
95 views
Weakly directive VHF/UHF antenna
Most resources around the internel discuss common antena types, classifying them between directive (like Yagi) and nondirective (like a simple dipole). Directive antennas are good when you know from ...
1
vote
0answers
76 views
2GFSK 9600bps Transmitter and amplifier for 433 MHz
I'm looking for a reliable, however cheap solution for ground-space communication. I need at least 50W of transmitted power with 2GFSK modulation at 70cm band (433 MHz). Transmission will be done ...
3
votes
2answers
99 views
Do MRI machines use the ISM band, and do they generate audible CW signals?
I've recently had an MRI, and after studying chapter two and three of the ARRL manual, I've got a better understanding of how my MRI machine might have worked.
Now, I am curious to know what would ...
2
votes
1answer
76 views
Embedded Message on Zastone ZT-X6 / WLN KD-C1
I recently got a couple of very basic Zastone ZT-X6 2W UHF handheld radios. The actual brand seems to be WLN and the model KD-C1 (because the programming software I downloaded from Zastone is named ...
2
votes
1answer
160 views
How to use 70 cm WiMo phasing harness for a COTS crossed yagi antenna?
In order to generate circular polarization in a crossed-yagi, a 90° phase delay is required between the horizontal and the vertical antenna. In practice, this is achieved either by making a mechanical ...
5
votes
1answer
136 views
Antenna for receiving 868MHz rocket telemetry: QFH(QHA), Helical, or?
I'm building a radio communication system for an amateur rocket project. We've decided to use LoRa 868MHz system. My question is, which antenna for the ground station will be the best choice? We're ...
1
vote
1answer
76 views
Why does signal power drop every night?
I have been monitoring power of a P25 control channel (at about 850MHz). For awhile, 24 hours a day. I graphed the power over a couple of weeks and it is almost sinusoidal, decreasing significantly ...
1
vote
1answer
95 views
Is it possible to make antenna for one specific frequency?
I have a GSM Modem that works on 2300MHz Frequency (LTE), but it could only receive 3 bar of signal strength.
I plan to make a DIY directional antenna that is made specifically for this Frequency ...
3
votes
2answers
211 views
It it really useful to terminate unused 75Ω outputs on a coax splitter?
When discussing improvements to my home HDTV Antenna/distribution system a colleague brought up the need to terminate all coax, even unused splitter ports.
My understanding of the way terminator ...
1
vote
1answer
79 views
Repeater for 1/4 square mile campus
I am a noob to a lot of amateur radio and I am investigating and planning a repeater setup to be installed in my workplace. We are on a hospital campus in Chicago, IL and have many tall buildings ...
1
vote
2answers
91 views
Repeating UHF Handheld via UHF vehicle transceiver
I have recently taken on programming radios for my workplace in Chicago, IL. We have an old base station (Kenwood TK863G-1) that I wanted to know if it would be possible to use as a repeater similar ...
1
vote
2answers
70 views
Help with ZaStone D900
I ordered a ham radio from eBay (doesn't matter which one) and I have gotten a completely different one than what I ordered. I'm quite new to amateur radio so please excuse my innocence/idiocy. I ...
2
votes
2answers
106 views
4G extension cable and antenna height?
I have recently bought a 4g Sim Card Router (TP-Link mr6400) and a 4g exterior LTE Antenna. With testing I have now doubled my connection speed. To go one step further, I am looking at the possibility ...
1
vote
1answer
507 views
Impedance matching between antenna and load - Theory and Practice?
I'm trying to do impedance matching between my PCB antenna and my circuit. My PCB antenna has a measured impedance of 49.4 - j8.1 ohms. The operating frequency is 915 MHz. The goal of matching is to ...
2
votes
1answer
80 views
why does net control hear a check-in which I do not hear?
Sometimes on a net, net control acknowledges a check-in that I haven't heard. That is, I hear some check-ins but not others. Not poor signal, just silence. But net control hears it.
Why might that be?
...
1
vote
2answers
135 views
What wireless communication technologies can travel long distances with a high bandwidth?
I couldn’t find a better place to ask this question, so I have asked it here.
I am looking to transmit and receive internet connectivity wirelessly over a distance of 6 miles (9.7 km) with a minimum ...
1
vote
1answer
67 views
RF inert adhesive for building antennas in the UHF to low GHz region
I want to experiment with different mechanical designs for some Yagi antennas for 440 MHz through perhaps 2.3 GHz. I am looking for some adhesives and/or potting-like materials that would be ...
3
votes
1answer
241 views
Relations between bit rate, frequency deviation and channel filter bandwidth
I just started using a couple of low power radio modules in my project (HopeRF RFM69HCW).
I made them work; they successfully transmit messages in a limited range (5-10 meters). Now I would like to ...
1
vote
4answers
1k views
Turn 75 Ω TV “Rabbit Ears” with a balun into a 50 Ω dipole antenna
I got myself a TV "Rabbit Ears" module originally for a TV. It came with a small length of coax, permanently attached to the antenna foot, and a Belling-Lee connector on the other end.
My idea was to ...
5
votes
4answers
363 views
TV strong station has no signal when coax is connected
Right, not directly ham radio related, but this puzzles my ham brain. I have several TVs connected to a distribution amp connected to an outside antenna. All but one work fine, and the one won't ...
2
votes
1answer
726 views
What parts / procedure do I need to build a UHF receiver that can connect to a standard pair of headphones
I have a low power wireless microphone (10 - 50 mW) with a large receiver designed to connect to a mixer/sound system. The mic transmits in the UHF band between 530 and 860 depending on the band (see ...
3
votes
3answers
424 views
Why is VHF better than UHF in this situation?
One of the sample questions for the British foundation level test is:
An amateur has the choice of VHF or UHF for a particular contact of some 25km. Which statement below best describes his choice?
...
2
votes
1answer
362 views
Why is 431-432MHz forbidden for use in London?
The band plan says:
Location Restriction: In addition it is very important to note that the band between 431-432MHz is not available for use if you are located anywhere within a 100km radius of ...
3
votes
2answers
341 views
Noticeable difference between trunk and roof mount?
Between trunk-mounting and roof-mounting a 2m/70cm antenna, both as through-hole NMO mounts, is there really that big a difference performance-wise? I mean, I know roof mounting is better, but let's ...
1
vote
1answer
299 views
2m loop with sense antenna for DF
I would like to construct a 2m Loop with a sense antenna. I have built just a loop antenna with great success that is resonant at 2m finding null's works quite well on local repeater outputs.
I would ...
2
votes
1answer
77 views
Help with small dish antenna on 2m/440
I have an oblong dish network antenna that I want to convert to 2m/440 usage.
I have seen the one for the 14 foot dish but I do not have one. Not sure if I should wind a coil and mount it in the ...
4
votes
1answer
171 views
Could UHF Earth-Satellite-Earth bouncing of signals off of this large metallized foil satellite be feasible?
The July 14, 2017 NASA Spaceflight article Soyuz 2-1A launches with Kanopus-V-IK and over 70 satellites says:
Mayak is a three-unit CubeSat which was built by Tvoii Sektor Kosmosa – or “Your Sector ...
3
votes
3answers
534 views
Can 2 uhf beam yagi antennas be used on a transmitter to get a diversity effect?
I'm having a problem getting a good signal up to a repeater site on UHF. I'm running 20W in a neighborhood with lots of trees, and the signal is fading in and out due to trees and the wind.
I can't ...
1
vote
2answers
132 views
V/U Packet Rate Limits
I'm studying for the General exam and I've encountered some questions about maximum baud rates on various bands. They seem... extremely optimistic. Given the trouble I've had investigating 9600 baud ...
3
votes
2answers
687 views
Are chokes necessary for VHF and higher frequencies?
I am trying to install a VHF/UHF antenna on my truck, and I have been studying everything I need to do that. I keep reading about chokes, in particular here: http://www.k0bg.com/choke.html
However, ...
3
votes
1answer
346 views
What is this Morse code-like station?
I’m trying to identify this signal at 928.807 MHz. A sample of the raw I/Q from gqrx is here (9.2 MB, .wav, 48000 Hz) and this is the waterfall:
I’ve tried decoding some common digital modes (...
1
vote
3answers
341 views
High SWR on a Jeep with Spare Tire Mount
I just installed a spare-tire mount and Browning BR-180 dual band antenna on my Jeep JK. Initial SWR testing show nothing higher than 1.4:1 across both bands so I didn't try to tweak it.
Then I put ...
9
votes
4answers
662 views
How does VHF/UHF propagate beyond the expected (radio) horizon?
I am not asking about the fairly well-known effect of the earth "appearing less curved to radio waves" that are otherwise still essentially line-of-sight, but a deeper arcanum:
In the ARRL Antenna ...
12
votes
3answers
6k views
Where are the baluns for VHF and higher? How can one be made?
In another question, commenters recommended that I look into adding a 1:1 balun to a dual-band dipole to eliminate the feedline as a radiator. As I understand it, a 1:1 balun also functions as a choke,...
2
votes
1answer
187 views
Realistic UHF noise floor when receiving signal from moon - 433 / 2400MHz
Let's imagine we're at ground station trying to receive UHF signal transmitted from moon at 433 / 2400 MHz. Our antenna with 25dB gain (circular polarization) points to the moon. Our LNA has 1dB NF.
...
7
votes
2answers
986 views
Moon->Earth 433MHz link achievable digital bandwidth
Let's assume we have the following situation:
Transmitter on moon orbit (distance from earth ~400'000km), around 433Mhz.
Transmitter power 1W, antenna gain 10dB, circular polarization. Steered to ...
5
votes
5answers
938 views
Can 433 MHz amateur bands be used for ISM purposes?
From this poster,
http://info.tek.com/AM-RSA306-Spectrum-Poster.html,
it indicates that a band around 433 MHz is globally-accepted for use as an amateur band.
Can this same band be used for ...
3
votes
2answers
4k views
Licensing a group of BaoFeng BF-888s in the UK
I've purchased a couple of BaoFeng BF-888S's for personal use with friends.
I've been told these radios can't be used legally without a licence and given the usage, I doubt I could faithfully even ...
0
votes
1answer
124 views
Using 'amodem' to transfer digitally using a UV5R
I reviewed docs for amodem, and it looks like I can send files and possibly other things with this.
I should only need to prep my computer as per the doc and set VOX correctly. Does anyone have ...
3
votes
2answers
353 views
How does the antenna noise temperature vary with antenna elevation?
I'm using a 14 element cross Yagi antenna in my system. For my link budget calculations, what antenna noise temperature should I consider? How does this vary with elevation?
1
vote
0answers
50 views
How to connect a motorola RVA50UL with MR350?
Currently I use a Motorola MR30R radio in the frequency 20 (462,6750 Mhz) with Interference Eliminator Code 59. I also have a Motorola RVA50UL, according to the manual, the frequency will be available ...
7
votes
6answers
12k views
Is packet radio possible on Baofeng UV-5R and similar HTs?
I am curious to know if it is possible to do packet radio on VHF/UHF using the UV-5R... I have seen some invasive hardware hacks, but without modifying the radio itself (firmware, hardware) it's my ...
8
votes
3answers
4k views
receiving AM radio station on UHF frequency
I'm studying for my Technician license, and listening in to HF, VHF and UHF bands just to get a feel for how to work with frequencies, squelch, antennas, etc. Had something happen today that I ...
