Questions tagged [uhf]
Ultra High Frequency is the frequency range 300-3000 MHz.
111
questions
0
votes
1answer
19 views
Obtaining S parameters using S11 measurements?
Is it possible to obtain the S-parameters of a circuit with only S11 measurements (S11 measurement with a VNA)?
My gut tells me that it should be possible by connecting open, short and characteristic ...
0
votes
1answer
28 views
Hatch Mount Antenna Selection - Dual Band 2m/70cm
I just bought a Diamond CP-5NMO hatch/lip mount and intend to put it on the hatchback lip of our 2018 Subaru Forester and, if it will fit, another one on our 2019 Kia Niro EV. I understand that hatch ...
1
vote
1answer
17 views
What length and number of radials should be used for a dual band vertical whip backpack antenna?
The Situation:
Very new Ham
I have a 2m/70cm 48" Abree whip antenna, originally designed to be connected directly to an HT
I would like to mount this antenna to the side of my hiking backpack, ...
0
votes
1answer
39 views
Can I slant-polarize a bay antenna?
I am trying to work a 700mhz LTE signal with a DB2 uhf bowtie television antenna. I find the cellular signal to be horizontally polarized. Can the bowties simply be twisted 45 degrees in both ...
1
vote
1answer
99 views
440MHz collinear dipole array - suitable coax?
friends!
Finally found my next antenna project..a collinear dipole array for the 70cm US ham band.
The general idea:
(image courtesy https://link.springer.com/referenceworkentry/10.1007%2F978-981-...
3
votes
3answers
171 views
Ground-Plane radial sizing, is there such thing as too long?
I'm just trying to make sure I understand the theory correctly.
I have some triband VHF/UHF/800MHz antennas, I need to mount on a tower so I plan on using a "mobile to base" conversion kit. ...
1
vote
1answer
108 views
Double Cross Dipole antenna for 437 MHz don't tune
I'm building a Double Cross Dipole antenna for 437 MHz to be used with a SDR receiver for CW cubesat.
The idea is to follow this "classic" paper from Gerald Martes, KD6JDJ.
I tuned every single dipole ...
0
votes
1answer
100 views
Outdoor Terrestial Digital TV Receiver Antenna: 500-700 MHz Band, Can I Make It Work Better?
See the unconventional antenna shown below, The whole antenna is made of two mirror-imaged Alum metal stampings on either side of a 2-cm hollow 31-cm long rectangular plastic boom. The antenna top and ...
0
votes
2answers
42 views
How Duty cycle affects transmission rate in RF module?
I planning to use RF module for communication of high precision GNSS module. So I am doing detail study on RF module. In one of the datasheets of RF module (part no: RFD868ux) mentioned that 'Duty ...
1
vote
2answers
44 views
RF PCB Design Difference Between Controlled Impedance Track and Impedance Matching Circuit
Im new on RF circuit designing. Im designing an circuit with GSM and GPS capabilities. I know when using high frequency signals the RF traces must be impedance matched. Now what I understand is, I can ...
6
votes
4answers
361 views
Any reason not to choose a discone antenna over a Wide/ MultiBand mobile antenna for TX/RX operations
We are setting up a all-band radio in an emergency com center that's intended most for amateur band use, but since its' for emergency use will also be used in the public safety bands; (150-170)MHz, (...
3
votes
1answer
126 views
Grounding for lightning safety - upper floor (UHF/microwave antennas)
I have some UHF, microwave antennas and an antenna rotator on a roof mounted mast. The "radio room" is in the second floor just below the antennas. Also the service entrance for building electricity ...
1
vote
1answer
133 views
how does this collinear antenna work?
I was looking for a cheap and easy to build 2M/70cm vertical. I found this: http://vk2zoi.com/articles/dual-band-high-gain-flower-pot/
Here are the plans to build it:
But I don't really understand ...
5
votes
2answers
871 views
World wide Radio Module
currently I am involved in a project were a data link is needed to communicate different devices. This is in one to many configuration and the devices are stand alone.
For this project there is need ...
0
votes
1answer
46 views
HopeRF in Narrow Band
I am new in this group, and I would first like to say thanks to this community, I have used the Stack groups to solve many many questions I have, so it is a powerful knowledge place. So thanks for ...
1
vote
1answer
85 views
Handheld multiband radio for a ham firefighter?
I live half a mile from my volunteer fire station. We are toned out on a VHF frequency by a neighboring municipality, and we provide mutual aid for their fire department that is toned out on an 800-...
2
votes
5answers
163 views
Optimal length of HT antenna for VHF UHF and diminishing return
I see folding antennas of various lengths that people are using for for their HT. My question is about the optimal length. I know it may "depend" on many factors so let me know if I need to provide ...
3
votes
5answers
264 views
Malicious interference to repeater
Our local repeater is severely sabotaged by unknown parties. For example, broadcast radio transmissions are repeated. Other times someone will send a transmission, when a qso is in progress. Local ...
3
votes
2answers
74 views
What VHF & UHF frequencies are important during an emergency?
If something bad goes down (state-wide or nationwide), what frequencies should I be tuning into?
I did see this answer, but I have a BaoFeng UV-82HP which cannot do HF at all, so what are my options?
...
1
vote
3answers
113 views
can I still hear a frequency if I can only tune in 5 kHz off?
I'm trying to listen in to the telemetry frequency for Wallops Island which is 411.325 MHz.
When I punch this into my radio (Baofeng UV-5R), the closest I can get is 411.320 MHz.
Will I still be ...
1
vote
2answers
572 views
GMRS not transmitting within a half mile
I recently got my GMRS license from the FCC, and I wanted to try out a couple radios for hiking and emergency communication. I have two tenway UV-5R pro radios (these do have an FCC ID) that are set ...
3
votes
1answer
72 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
155 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
645 views
Why arenāt emergency services using callsigns?
Iām 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
815 views
VHF 50 Ī© Antenna Over 75 Ī© TV Coax
I have a 50 Ī© VHF airband antenna which Iām 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
391 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
514 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
477 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
137 views
Weakly directive VHF/UHF antenna
Most resources around the Internet discuss common antenna types, classifying them between directive (like Yagi) and nondirective (like a simple dipole). Directive antennas are good when you know from ...
1
vote
0answers
98 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
115 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
174 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
394 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 90Ā° phase delay is required between the horizontal and the vertical antenna. In practice, this is achieved either by making a mechanical ...
5
votes
1answer
202 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
79 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
153 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
1k views
It it really useful to terminate unused 75Ī© 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
94 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
110 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
93 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
427 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
2answers
834 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
86 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
141 views
What wireless communication technologies can travel long distances with a high bandwidth?
I couldnāt 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
91 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
427 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
2k views
Turn 75 Ī© TV “Rabbit Ears” with a balun into a 50 Ī© 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
511 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
1k 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
557 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?
...
