Questions tagged [uhf]
Ultra High Frequency is the frequency range 300-3000 MHz.
122
questions
0
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0answers
43 views
Sub GHZ Audio transmission with radiohead library
Can I use sub-ghz (433 Mhz) to transmit audio.I already used radiohead library with RFM96 to transmit small packets of data and built a point to point mesh chat application.
Now i wanted to test FSK ...
5
votes
0answers
167 views
Hardened UHF Antennas
Minuteman missile silos used an interesting hardened UHF antenna.
What kind of antenna is this? Does anyone have a drawing with a cross section?
Edit:
Jay Moore added a picture to a different type of ...
1
vote
2answers
61 views
Is power output or something else to blame for my duplexer failing?
A Ham buddy of mine and I were trying to setup a UHF repeater in our area due to a lack of them. We had two Motorola CDMs, one a 1250 and one a 1550, and we purchased a $200 or so reject only duplexer ...
2
votes
2answers
155 views
How much dB gain do you need from an LNA in front of an antenna for great low-signal reception from satellites in the 2m and 70cm bands?
We are building a multi-stage LNA for a TR module we are building in the 144MHz and 440MHz range. This LNA we are considering (Qorvo QPL9547) provides about 22dB gain in the 2m and about 27dB in the ...
4
votes
2answers
175 views
Stacking Two UHF Yagi Antennas
Aloha!
I have two HYS TC-YG05 Yagi antennas that were gifted to me and I would like to stack them side by side ( Collinear), in the vertical orientation for some local weather balloon telemetry data ...
3
votes
1answer
65 views
Is it possible to convert a euro Yaesu 991a to US band plan?
I bought a euro Yaesu 991a . The vhf/uhf band plan is severely limited for use in the US . I have tried the button presses as shown for the earlier 991 and the service mode works to open the frequency ...
5
votes
1answer
235 views
Failing to detect Hydrogen line with 105cm dish
I've seen many examples of roughly 1 metre sized dishes being used w H+ sawbird and an SDR to detect and analyze Hydrogen line signal, and have been trying myself but can't seem to get anything beyond ...
4
votes
3answers
422 views
Is testing SWR *practically* less important for 2m/70cm than HF bands?
Totally new amateur operator and I've noticed that a lot of material e.g. Your Tube videos, blogs, forums when discussing metering VSWR mainkly seem to be talking about HF bands. I also see fewer VSWR ...
2
votes
0answers
60 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
321 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 ...
1
vote
1answer
109 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 ...
0
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1answer
58 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
56 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
131 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
44 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
447 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
973 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
173 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
205 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
88 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
110 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
1k 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
193 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 ...
2
votes
1answer
1k 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
887 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
50 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
100 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
6answers
2k 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
450 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
388 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?
...
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3answers
122 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
853 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
81 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
253 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
706 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
905 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
834 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, ...
6
votes
2answers
900 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
764 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
157 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
116 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
136 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
232 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
578 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 ...
6
votes
1answer
291 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
84 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
289 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 ...
4
votes
3answers
3k 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
102 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
130 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 ...