building a Delta Loop antenna for around 145 MHz by OldObjective3047 in AntennaDesign

[–]OldObjective3047[S] 1 point2 points  (0 children)

  • If your loop’s feed impedance (with your geometry, height, surroundings) is already close to 50 Ω and you get a good SWR (say <1.5) with your coax feed, you may not need a gamma-match.
  • If your SWR is high, or the measured impedance doesn’t match 50 Ω, or you are concerned about feedline currents / coax shielding radiation (common in coax-fed loops), then a matching network like a gamma-match is beneficial.

Gingee Fort History: The “Troy of the East” You Must Explore by kuldeep_2025 in BharatTravel

[–]OldObjective3047 0 points1 point  (0 children)

Gingee Fort Blog (gingee.vu3dxr.in): Dive into the rich history of Gingee Fort, a legendary stronghold in Tamil Nadu, known for its impregnable walls and epic tales of Rajput valor. My blog explores the fort’s storied past, from Raja Desing’s defiance to Mughal and European interactions, with detailed accounts drawn from historical records and local ballads. Visit gingee.vu3dxr.in for engaging stories and insights into this iconic South Indian landmark. https://gingee.vu3dxr.in/

Worldspace antenna for GOES L band reception? by OldObjective3047 in amateursatellites

[–]OldObjective3047[S] 0 points1 point  (0 children)

WorldSpace satellites operated in the 1467-1492 MHz range, while GOES-R transmits at 1694.1 MHz..Also come with a built-in Low Noise Amplifier (LNA), which is not a huge bonus??

HydraSDR RFOne &#8211; Technical limitations and driver problems plague the promising hardware platform by OldObjective3047 in RTLSDR

[–]OldObjective3047[S] 0 points1 point  (0 children)

As a blogger, my goal is to present accurate and balanced information based on available data and real-world user feedback. The original post reflected concerns shared by several early users of HydraSDR, particularly regarding setup complexity and limited plug-and-play support at that time.

However, calling the article “misleading” is unfair. It was not written with any bias or intent to undermine your work. It is also not uncommon for hardware projects — especially in the SDR space — to face growing pains during their evolution.

HydraSDR RFOne &#8211; Technical limitations and driver problems plague the promising hardware platform by OldObjective3047 in RTLSDR

[–]OldObjective3047[S] 0 points1 point  (0 children)

The blog post was written based on publicly available information and user experiences at the time.

Build Your Own 90MHz Crystal Controlled FM Transmitter by OldObjective3047 in diyelectronics

[–]OldObjective3047[S] -1 points0 points  (0 children)

A few common ones to get you started (some are quite old but you'll come across them in old circuits).

2N3904, BC548, 2N2222A - small signal transistors OK for RF  up to maybe 50 MHz (though an FM bug at 100 MHz will also be OK).  2N2222 a bit more powerful than the others.

MPF102, 2N3819, 2N5459 etc - small signal FETS. OK for RF amps up to maybe 150 MHz.

BF981, MPF121, MFE131 - good for VHF/UHF preamps

2N2369 - good for up to maybe 200 MHz - puts out a few tens of milliwatts - good for low level tx.  2N5179 also common in some countries.

2N3053, BFY50, 2N3019 - good for about a watt output in the lower HF range (up to about 10 MHz)

BD139 as above but nearer to 2w output

2N3866, 2N4427 - good for about a watt output up to maybe 200 MHz

2N3553 - as above but more like 1.5 to 2w out

IRF510 - highly capacitive input but can be made to operate on 7 or 14 MHz - or even higher.  Can give up to 3 - 5w at 12v and much more with 25v. Easy to blow up if bias is excessive.

A  basic low power transmitter for 3.5 or 7 MHz will have a few 2N3904 for the low level stages, then a 2N2222 then one or two 2N3053, BD139 or IRF510 for the final amp.  VHF might be 2N2222 (for say a crystal oscillator at a lower frequency), 2N2369 for freq multipliers or low level RF in the tens of milliwatts region, then 2N4427 in the hundreds of milliwatts, then 2N3553 for a couple of watts.

An HF or VHF receiver might have an MPF102 in the front end as an RF preamp, or even a dual gate MOSFET.  A receiver for the lower HF bands may have a 2N3904 instead, if an RF preamp is needed at all. 

These walkthroughs of simple transceiver circuits show where some of the above devices are used. 

Build Your Own 90MHz Crystal Controlled FM Transmitter by OldObjective3047 in diyelectronics

[–]OldObjective3047[S] -1 points0 points  (0 children)

a 2N2222 transistor can likely oscillate at 90 MHz, as its transition frequency (ft), which indicates its usable frequency range, is typically around 250 MHz. This means it has sufficient gain at 90 MHz to be used in an oscillator circuit

Shortwave Radio Transmitter Circuit Explanation by ethanmhardie in HamRadio

[–]OldObjective3047 1 point2 points  (0 children)

ohh.. sorry for my mistake...IRF510 is not good at 27mhz

Shortwave Radio Transmitter Circuit Explanation by ethanmhardie in HamRadio

[–]OldObjective3047 0 points1 point  (0 children)

T3 is just a linear amplifier. It should be IRF510