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Questions tagged [uhf]

Ultra High Frequency is the frequency range 300-3000 MHz.

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Does sporadic E apply to UHF?

ES season is coming up so I want to know if ES applies to UHF. Google says that it applies to 6 meters and 2 meters. What about 70 centimeters? Can I talk further with 8 watts? They say you can DX and ...
o'o's user avatar
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1 vote
2 answers
115 views

What is this pulsating signal?

When scanning through UHF, I find that there are a few frequencies that made a sound similar to a fast drum (~300 bpm?) Here are a list of the frequencies: 451.200 MHz 454.280 MHz more coming soon ...
o'o's user avatar
  • 392
0 votes
1 answer
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Converting a 470-694Mhz TV antenna for 433Mhz reception

I'm working on a project which requires me to pick up LoRa signals that will be transmitted from a relatively low gain antenna. I've figured out that a large dipole would be idea for the receiver ...
Hristos's user avatar
0 votes
1 answer
95 views

RF Coax Termination Question

I am looking to terminate a line with the below characteristics and having a hard time locating an RF coax terminator. Can anyone help? I have an FPGA HW that is feeding multiple receivers. The input ...
Newb's user avatar
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1 vote
1 answer
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Entel HT880 Programming Help Needed

I'm a new HAM member in this awesome community, so please take everything with a grain of salt. First of all, I DO NOT want any CPS programs! Just wanted to make that clear. Recently, I've received a ...
H.M Rezoan Duranto's user avatar
1 vote
0 answers
97 views

why i cant hear my voice when i connect to two Baofeng uv82 to the same repeater frequencies

I have two baofeng uv-82 and I connected both to the same repeater frequency, and once I press the ptt button I can hear the squelch sound on both radios. However, once I talk to one radio, I don't ...
khaled majali's user avatar
1 vote
1 answer
649 views

I am trying to get the 800.00 frequencies on a Baofeng UV-5R

I am trying to use my Baofeng radio as a police scanner and all the frequencies are in the 800.000 frequencies. Example: I am putting 851.1500 into the “scanner”, but the Baofeng radio is not ...
Keith Lagrave's user avatar
1 vote
2 answers
122 views

Optical line of sight over long distances?

Is there a way to use radio to restrict communication to optical line of site at distances greater than 10 miles? For example, the signal is transmitted directionally from a mountain top fire lookout, ...
W6M's user avatar
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2 votes
2 answers
120 views

Long Distance antenna feedline for UHF/2.5GHz signal

I'm building a boat towed underwater platform. This underwater platform has a single board computer with a remote wifi antenna connection via a u.fl connector. I'm experimenting around with a way to ...
leeprevost's user avatar
4 votes
0 answers
60 views

Optimizing Half-Duplex Sequencing: Consolidating RF and Power Connections with Bias-T and VOX

I've successfully implemented a half-duplex sequencing mechanism, which I've illustrated below. The outdoor components are represented in green. In my current setup, I utilize a PLC to control both an ...
Moses Browne Mwakyanjala's user avatar
1 vote
1 answer
220 views

Creating a single feed wearable wire antenna

When I was deployed, our commo guys gave us wire antennas we could thread through our body armor (through the MOLLE loops). These antennas were just lengths of 50Ω coax that had the insulation ...
Jesse Knott's user avatar
6 votes
3 answers
850 views

Is a boom important to a Yagi?

I am trying to make a yagi for a 900M. The tinkering starts causally with some 1.2mm welding wire (cut to size based on K7MEM yagi calculator, direct soldering, no special matching as suggested on ...
Ben's user avatar
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2 votes
1 answer
180 views

UnUn for VHF and UHF

Is it possible to build an UnUn for VHF or UHF like in HF? Goal is to use a simple endfed wire or piece of metal as an antenna. EDIT: I meant "endfed halfwave".
microfox's user avatar
-1 votes
1 answer
163 views

How to build the best bang for yhe buck uhf vhf antenna or should i just buy one [closed]

Help with antenna build what makes up a great antenna what can I use for elements and would a dush network dish be good reflector and how to wire the elements like the copper to one side and the ...
vanny tran's user avatar
5 votes
4 answers
408 views

UHF 70cm unlicensed use

We are farmers with (edit) 25-40w radios mostly old Kenwoods and Motorolas in all of our tractors and vehicles. I'm not exactly sure what frequency we have but the man who programmed them set them up ...
Logan's user avatar
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2 votes
3 answers
811 views

Baofeng UV-5R: Severe static/interference on UHF frequencies

I have a U5-5R, which I've set up to use (among other things) the analog (NFM) frequencies of the PMR446-band. I've been using it with the stock (136-174/400-520MHz) antenna and a monophone connected ...
razumny's user avatar
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0 votes
1 answer
111 views

Commercial UHF bands in Sweden

I was investigating satellite (onboard) UHF transmitters. Some of them support commercial and amateur bands. To my understanding, amateur bands span between 430 to 440 MHz and commercial UHF between ...
Moses Browne Mwakyanjala's user avatar
1 vote
2 answers
203 views

Can an antenna be affected if mounted to a bull bar?

When I say 'mounted to a bull bar' I mean the antenna being metal on metal contact to the bull bar without any rubber or fiber glass keeping the materials from touching. Could this affect the ...
bailey707's user avatar
2 votes
1 answer
98 views

Looking for specifications for Wilson Electronics WAU 420 amplifier

Hey there helpful people I'm trying to track down some specifications on a Wilson Electronics WAU 420. I have no idea on its exact age but guessing its from the late 90's. It's likely UHF band and ...
Rowan Hawkins's user avatar
1 vote
0 answers
75 views

Design of an LNA housing box for a UHF/VHF satellite ground station

I'm currently designing a waterproof metallic case to house LNAs, power cables, and RF switches for a UHF/VHF satellite ground station. As shown in the diagram below, the antennas are connected to an ...
Moses Browne Mwakyanjala's user avatar
1 vote
1 answer
141 views

Would a transmitter similar to "The Thing" be legal on ham bands in the US?

The Thing was a listening device used by the Soviet Union to eavesdrop on US government officials. It was basically an AM transmitter if I understand correctly, but it required another transmitter on ...
Someone's user avatar
  • 604
1 vote
3 answers
187 views

RF switch for half-duplex sequencing on amateur UHF satellite ground station

I need a 3-port RF switch illustrated below. The idea is to use this switch with a sequencer to enable half-duplex communication on a UHF antenna. The switch has three ports: port A connected to the ...
Moses Browne Mwakyanjala's user avatar
0 votes
1 answer
189 views

YouLoop antenna for amateur satellite reception

I recently learned about the commercial YouLoop antenna and it seems to be quite simple to set up. They said it was possible to receive satellite signals on amateur VHF (e.g. NOAA and other CubeSats ...
Moses Browne Mwakyanjala's user avatar
5 votes
3 answers
1k views

What kind of soldering iron is best for PL-259 (UHF) connectors?

What do you use to solder connectors onto bulk coax cable? Soldering the UHF connector to the coax shield on a PL-259 is described as requiring a bit of "experience and skill" in Dave Casler'...
Dax's user avatar
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0 votes
1 answer
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Correct terminology for a repeating radio transmission

I am using 'active radio tags' in a particle tracking experiment. The tags emit a 433 MHz signal containing a unique ID code at a programmable time interval and I am attempting to locate them by ...
Jenks23's user avatar
3 votes
0 answers
316 views

Turnstile antennas with a "single-point feed": what's the antenna theory behind this, and how do I build/model it?

The conventional turnstile antenna uses a 1/4wl phasing line between the crossed elements, to get the required phase shift. 4nec2 includes an example file, though, of a circularly-polarized Yagi using ...
1200bps's user avatar
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1 vote
0 answers
134 views

Need help in the fabrication of an UHF power amplifier

I recently decided to conceive a 10W class 446MHz amplifier. I want to be able to amplify a 100mW signal into a 10W, for that i'm going for a two stages amplifier : SKY65162 to amplify the signal to ...
Wireless Learning's user avatar
0 votes
0 answers
118 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 ...
Asif Rahman's user avatar
9 votes
1 answer
457 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 ...
Olg's user avatar
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1 vote
2 answers
158 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 ...
Caleb Krajnak's user avatar
2 votes
2 answers
703 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 ...
KJ7LNW's user avatar
  • 723
4 votes
2 answers
2k 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 ...
RF101's user avatar
  • 41
3 votes
1 answer
1k 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 ...
rocco's user avatar
  • 31
5 votes
1 answer
342 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 ...
Jack_SH's user avatar
  • 51
4 votes
3 answers
2k 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 ...
Jason Tan's user avatar
  • 151
2 votes
0 answers
129 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 ...
FontFamily's user avatar
1 vote
2 answers
2k 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 ...
Hayden Thring's user avatar
1 vote
1 answer
133 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 ...
Felipe Kalinski's user avatar
0 votes
1 answer
245 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 ...
divB's user avatar
  • 163
0 votes
1 answer
219 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 ...
William's user avatar
  • 803
1 vote
1 answer
369 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, ...
hehe3301's user avatar
  • 157
1 vote
1 answer
48 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 ...
Gary's user avatar
  • 11
1 vote
1 answer
2k 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-...
user avatar
4 votes
3 answers
4k 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. ...
Frank's user avatar
  • 349
1 vote
1 answer
401 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 ...
Carlo IU2KQB's user avatar
0 votes
1 answer
448 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 ...
user17230's user avatar
0 votes
2 answers
362 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 ...
BalkisMM's user avatar
1 vote
2 answers
146 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 ...
M.Toy's user avatar
  • 13
6 votes
4 answers
3k 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, (...
Frank's user avatar
  • 349
3 votes
1 answer
401 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 ...
rubund's user avatar
  • 224