https://www.reddit.com/r/bugs/comments/1w4ljkg/desktop_web_i_cannot_pm_anyone_three_little_dots/?

1. The Urea Cycle: A Four-Step Biochemical Engine

The Urea Cycle is a critical metabolic pathway occurring primarily in liver cells (hepatocytes). Its primary job is converting toxic ammonia—a natural byproduct of protein catabolism and intense physical exertion—into neutral, water-soluble urea that the kidneys safely excrete in urine.

High Energy Cost: The cycle is energetically expensive. Synthesizing a single molecule of urea consumes 4 high-energy phosphate bonds (equivalent to 4 ATP molecules).

Mitochondrial Entry Step: Ammonia and bicarbonate combine inside the mitochondria to form carbamoyl phosphate (consuming 2 ATP). Carbamoyl phosphate then joins with the amino acid ornithine to yield citrulline.

Cytosolic Transition: Citrulline leaves the mitochondria into the cytosol, where it reacts with aspartate to form argininosuccinate (consuming 2 more ATP equivalents), which is then cleaved into fumarate and arginine.

The Exit & Regeneration: The enzyme arginase splits arginine, releasing urea for renal excretion while regenerating ornithine to restart the cycle.

1. Ammonia Dynamics and Neurobiology

Ammonia readily crosses the blood-brain barrier. In healthy conditions, background levels are managed smoothly, but elevated systemic ammonia (hyperammonemia) directly disrupts brain biochemistry:

Astrocytic Swelling: In the brain, specialized glial cells called astrocytes absorb excess ammonia and combine it with glutamate to form glutamine via the enzyme glutamine synthetase.

Osmotic Shift: Accumulating glutamine creates an osmotic gradient, drawing water into astrocytes. This causes cellular swelling, low-grade cerebral edema, and neuroinflammation.

Neurotransmitter Imbalance: Depleting glutamate impairs excitatory signaling and cognitive processing speed, manifesting as "brain fog," reduced mental stamina, lethargy, and decreased attentional control.

1. Near-Infrared (NIR) Light & the Right Upper Quadrant

Applying Near-Infrared (NIR) light over the liver (the Right Upper Quadrant of the abdomen) is popular in biohacking contexts to support metabolic function, though several physical and biological distinctions are important to note:

Penetration Depth: NIR light in the 700–1100 nm wavelength range penetrates biological tissue roughly 1 to 3 centimeters. In most adults, the abdominal wall, subcutaneous fat layer, and peritoneum sit between the light source and the liver tissue, limiting the direct photons reaching liver mitochondria.

Photobiomodulation Mechanism: When photon energy does reach tissue, photobiomodulation works primarily by stimulating cytochrome c oxidase in the mitochondrial electron transport chain—boosting mitochondrial membrane potential and ATP output.

Non-Thermal Process: Photobiomodulation is non-thermal. It does not rely on heat to increase the kinetic energy of enzymes (such as argininosuccinate synthetase). Excessive thermal heating would denature enzymes rather than accelerate them.

1. Impact on Mental Focus and Deep Brain States

Reducing metabolic waste products creates a favorable biochemical environment for optimal central nervous system performance:

Reduced Neural Resistance: Clearing systemic metabolic load restores normal astrocytic volume and normalizes the glutamate-glutamine cycle. This reduces central fatigue and improves signal-to-noise ratios in cortical networks.

Focus and Trance States: While the concept of a "Hepatic Point" leading directly into a theta-wave state is an informal wellness concept rather than a clinically validated pathway, minimizing neurotoxic waste undeniably aids sustained attention, relaxation, and receptivity during deep meditative or hypnotic protocols.

https://frequencygeek.substack.com/p/how-i-got-rid-of-my-smart-meter

https://www.reddit.com/r/RadioQuietZone/comments/1voiwt9/censorship_hacked_phone_after_taking_screenshots/?

https://magdahavas.com/electrosmog-exposure/ground-currentstray-voltage/ground-current-videos/

July 27, 2016. I am going to post a series of educational videos that I am producing on the ground current pollution problem we are experiencing not only in Ontario but in other provinces and in other countries, like the U.S. Most people are unaware of this form of electromagnetic pollution. However, it is getting worse and needs to be dealt with. Ground current is a problem not only in some rural areas but in urban areas as well. We have considerable information about how it affects livestock, especially dairy cows. It also affects people and non-agriculture animals.

Attempts to bring in a private member’s bill in Ontario to resolve the ground current pollution problem has failed twice now, first in 2006 and again this year. I have no hope that this government is going to do anything useful about the ground current problem. Nor do I think a change in government will make any difference. Our electrical utility, that is responsible for much of this problem, is being sold to the private sector and I certainly don’t think they will spend the money to get the current out of the ground.

Animal care groups, like the OSPCA that have been informed about the problem, are choosing not to get involved. This issue has become a political hot potato that just gets tossed around with no real progress being made.

A few years ago when a dog got electrocuted during a regular dog walk, there was a great public outcry. But when an animal dies on a farm … it is quietly buried with the farmer having to bare the economic and emotional cost.

The consequence is that animals will continue to suffer and die. Some more farmers will go out of business and their children won’t inherit the family farm.

People care about animals and if they only knew how these animals suffer they would not stand by and do nothing. The problem is they don’t know. I hope these videos will create greater awareness.

The videos are meant to provide information about what is creating this ground current problem and why; the effects it has on dairy cows and other animals including people; and how the problem can be resolved.

Below are links to the videos I’ve created so far. I will continue to add to this blog as the videos come on line. Feel free to share the videos. As more people learn about this, and if the media continues to report on the problem, we may eventually alert someone in a position of authority who has the brains and the balls to do the right thing and get the current out of the ground and back onto the wires where it belongs.

For those of you who would like to watch the videos in order … click here to go to my play list on ground current or copy this url into your browser (https://www.youtube.com/watch?v=AhIPgdOt3SE&list=PLeE2iwAw4bXX13xabObZBea6-4jI95oXW)

PART 1: Introduction to Ground Current Video 1-1: Ground Current Pollution – An Introduction: https://www.youtube.com/watch?v=AhIPgdOt3SE

PART 2: Biological Effects of Ground Current Video 2-1: Ground Current – Affects Cow Behaviour: https://youtu.be/DScyoSbAiD4

Video 2-2: Ground Current – Affects Cow Health and Productivity: https://youtu.be/We5KoccWDGQ

Video 2-3: Ground Current – Affects Reproduction on Dairy Farms: https://youtu.be/KFlOtHz5R-E

PART 3: Frederick Earth Table: A Laboratory Demonstration of Ground Current at 60 Hz and at kHz frequencies. Video 3-1: Ground Current and the Frederick Earth Table at 60 Hz: https://www.youtube.com/watch?v=_C24l9ONKi0

Video 3-2: Ground Current and the Frederick Earth Table at kHz frequencies: https://www.youtube.com/watch?v=k7dlQxHfw6E

PART 4: Our Electrical Distribution System Video #4: How our electrical system works and why it is causing ground current pollution: in prep

More videos may follow.

Thanks for watching … and feel free to share.

Ground wave explained

Ground wave is a mode of radio propagation that consists of currents traveling through the earth. Ground waves propagate parallel to and adjacent to the surface of the Earth, and are capable of covering long distances by diffracting around the Earth's curvature. This radiation is also known as the Norton surface wave, or more properly the Norton ground wave, because ground waves in radio propagation are not confined to the surface. Groundwave contrasts with line-of-sight propagation that requires no medium, and skywave via the ionosphere.

Ground wave is important for radio signals below 30 MHz, but is generally insignificant at higher frequencies where line-of-sight propagation dominates. AM and longwave broadcasting, navigation systems such as LORAN, low-frequency time signals, non-directional beacons, and short-range HF communications all make use of it. Range depends on frequency and ground conductivity, with lower frequencies and higher ground conductivity permitting longer distances.[1]

Overview Lower frequency radio waves, below 3 MHz, travel efficiently as ground waves. As losses increase with frequency, high frequency transmissions between 3 and 30 MHz have more modest groundwave range and groundwave is unimportant above 30 MHz. Surface conductivity affects the propagation of ground waves, with highly conductive surfaces such as sea water providing the best propagation, and dry ground and ice performing the worst.[2]

As the distance increases, ground waves spread out according to the inverse-square law. The imperfect conductivity of the ground tilts the waves forward, dissipating energy into the ground.[3] The long wavelengths of these signals allow them to diffract over the horizon, but this leads to further losses. Signal strength tends to fall exponentially with distance once the Earth's curvature is significant. Above about 10 kHz, atmospheric refraction helps bend waves downward. Only vertically polarized waves travel well; horizontally polarized signals are heavily attenuated.

Groundwave signals are relatively immune to fading but changes in the ground can cause variation in signal strength. Attenuation over land is lowest in the winter in temperate climates and higher over water when seas are rough. Hills, mountains, urban areas, and forests can create areas of reduced signal strength. The penetration depth of ground waves varies, reaching tens of meters at medium frequencies over dry ground and even more at lower frequencies. Propagation predictions thus require knowing the electrical properties of subsurface layers, which are best measured from groundwave attenuation.

Applications Most low-frequency radio communication is via groundwave propagation. Groundwave is also the primary mode for medium frequencies during the day when skywave is absent, and can be useful at high frequencies at short ranges. Uses include navigation signals, low-frequency time signals, longwave radio, and AM radio. The increased effectiveness of groundwave at lower frequencies gives AM radio stations more coverage at the low end of the band. High frequency over-the-horizon radar may use groundwave at moderate ranges but skywave at longer distances. Military communications in the very low and low frequency range uses ground wave, especially to reach ships and submarines, as groundwaves at these long wavelengths penetrate well below the sea surface.

In the development of radio, ground waves were used extensively. Early commercial and professional radio services relied exclusively on long wave, low frequencies and ground-wave propagation. To prevent interference with these services, amateur and experimental transmitters were restricted to the high frequencies (HF), felt to be useless since their ground-wave range was limited. Upon discovery of the other propagation modes possible at medium wave and short wave frequencies, the advantages of HF for commercial and military purposes became apparent. Amateur experimentation was then confined to only authorized frequencies in the range.

Modeling In the 1930s, Alfred Norton was the first author to accurately describe groundwave mathematically, deriving an equation for field strength over a flat earth. Van der Pol and Bremmer published calculations for a spherical Earth from 1937 to 1939. Later work focused on paths with variable conductivity, the effects of terrain and objects on the ground, and computer modeling.

Related terms Mediumwave and shortwave reflect off the ionosphere at night, which is known as skywave. During daylight hours, the lower D layer of the ionosphere forms and absorbs lower frequency energy. This prevents skywave propagation from being very effective on mediumwave frequencies in daylight hours. At night, when the D layer dissipates, mediumwave transmissions travel better by skywave. Ground waves do not include ionospheric and tropospheric waves

Notes and References

Book: Handbook on Ground Wave Propagation . Angulo I, Barclay L, Chernov Y, Deminco N, Fernández I, Gil U, Guerra D, Milsom J, Peña I, De la Vega D . . 2014 . 978-92-61-18661-6 . Geneva, Switzerland . PDF . 23 July 2024.

Book: Introduction to Wave Propagation, Transmission Lines, and Antennas . September 1998 . Naval Education and Training Professional Development and Technology Center . Naval Electrical Engineering Training, Module 10 . 2.16 . Chapter 2: Ground Waves . NavEdTra 14182 . http://www.tpub.com/content/neets/14182/css/14182_76.htm .

PDF (archive zipped) . https://web.archive.org/web/20180511150057/https://www.dralos.com/downloads/united_states_navy_navedtra%2014182.zip . 2018-05-11 . limited.

Ling . R. T. . Scholler . J. D. . Ufimtsev . P. Ya. . 1998 . Propagation and excitation of surface waves in an absorbing layer . live . Northrop Grumman Corporation . Progress in Electromagnetics Research . 19 . 49–91 . 10.2528/PIER97071800 .

https://everything.explained.today/Ground_wave/

https://magdahavas.com/from-zorys-archive/arctic-over-the-horizon-radar-a-othr-planned-for-ontario-farmland-kawartha-lakes-clearview-township/

May 2026: Two sites have been selected by the Department of National Defence (DND) for an Arctic Over the Horizon Radar site. The Transmitter site is scheduled for Kawartha Lakes and the Receiver site is set for Clearview Township with construction beginning in the winter of 2026. Dr. Magda Havas gave a talk in Creemore, Ontario on May 27, 2026. The handout (pdf) is available here for those interested.

Slides presented in Creemore for A–OTHR are available here as a pdf and here is a video.

Disclaimer: Information about military OTHR sites is often classified. Consequently, ability to verify some of the information provided by the DND and Artificial Intelligence (AI) is limited. This document summarizes some of the potential adverse human and environmental health effects of such an installation.

Note: In addition to radio frequency radiation (3-30 MHz), sites will generate ELF EMFs, dirty electricity, ground current and light pollution. Transmitter OTHR sites are often located at least 10 to 20 km plus from communities; and Receiver sites are at least 5 to 10 km plus away. These two proposed sites are MUCH closer to where people live and are going to be built on prime farm land near important wetlands.

Two additional sites are also planned for Ontario, although those locations have not yet been identified.

https://articles.andrew-doan.com/measure-body-voltage-in-minutes-with-this-easy-method/

[J] [Lyme] The Role of EMFs in EHS & Lyme Disease

https://www.reddit.com/r/Electromagnetics/comments/1vmfznq/j_lyme_the_role_of_emfs_in_ehs_lyme_disease/

Every patient I ever tested who had a diagnosis of electro-sensitivity turned out to test positive for Lyme

https://www.reddit.com/r/Electromagnetics/comments/3ek99o/every_patient_i_ever_tested_who_had_a_diagnosis/

[J] [Pathogens: Bacteria] Cell phones cause bacteria to become resistant to antibiotics (2019)

https://www.reddit.com/r/Immunology/comments/ippyt5/paper_found_cell_phones_causing_bacteria_to/

Wi-Fi causes bacteria to become resistant to antibiotics and to produce biofilm in which they can hide in (2019)

https://www.reddit.com/r/Immunology/comments/ippzxk/wifi_causes_bacteria_to_become_resistant_to/

Hypersensitivity to man-made electromagnetic fields (EHS) correlates with immune responsivity to oxidative stress: a case report (2024)

https://pmc.ncbi.nlm.nih.gov/articles/PMC11302546/

Moved from:

https://www.reddit.com/r/Electromagnetics/comments/1v9b7z5/starlink_meter_reports_wifi_green_bank_post/

u/ki4clz commented:

remind me again what the “m” is in relation to in dbm

for example:

dbd is db in relation to a dipole

dbi is db in relation to isotropic

dbmW is db in relation to ERP in MilliWatts - I think this is what you’re trying to convey, but I’m not 100% sure

for the kids in the back: a db or Decibel is a logarithmic scale used for many things that use wavelengths… so light, or sound, or radiowaves as they all for the most part follow The Inverse Square Law…

so when OP says he used a meter? to calculate the reception of a nearby signal that is… lets say -40dbmW that means the detector circuit is picking up 1x10^-4 mW before amplification… or 0.0001 mW of non-ionizing radiation in the form of a radiowave on one axis

which by comparison is 10,000,000,000 times (10Billion) times weaker than standing in direct sunlight (+60dbmW) getting your vitamin D on…

Fiber + Wi-Fi VS 5G router

https://www.reddit.com/r/Electromagnetics/comments/1vjsczy/fiber_wifi_vs_5g_router/p38z1qz/

[Fiber Optic] Why Do Fiber Optic Installations Increase Electrical Sensitivity? by Jeromy Johnson

https://www.reddit.com/r/Electromagnetics/comments/1ub1maj/fiber_optic_why_do_fiber_optic_installations/

Last week, I submitted instructions on how to turn off wi-fi on a fiber optic modem.

https://www.reddit.com/r/Electromagnetics/comments/1vfj4l6/wifi_how_to_turn_off_wifi_of_your_verizon/

[Fiber Optic] Fiber optic pulses while electricity is on. Back up battery in indoor router and back up battery on outdoor box pulse more after turning off electricity for the night.

https://www.reddit.com/r/Electromagnetics/comments/1vmgfkx/fiber_optic_fiber_optic_pulses_while_electricity/?

[Light: Flickering] Fiber optic lines flicker light through the walls.

https://www.reddit.com/r/Electromagnetics/comments/18jvf1h/light_flickering_fiber_optic_lines_flicker_light/

Joint wiki with r/targetedenergyweapons

[WIKI] Electronic Torture: Fiber Optic Internet

https://www.reddit.com/r/TargetedEnergyWeapons/comments/16dlj6e/wiki_electronic_torture_fiber_optic_internet/?

[WIKI] Fiber Optic: Optical Ultrasound

https://www.reddit.com/r/TargetedEnergyWeapons/comments/1e1rk62/wiki_fiber_optic_optical_ultrasound/

I purchased a house in the radio quiet zone. The prior owner had 3 fiber optic TV set boxes, fiber optic internet and fiber optic telephone. Though his account was terminated, the fiber optic lines pulsed. I asked the Spruce Knob to remove their 3 TV set boxes. I removed the fiber optic lines from my home except for two fiber optic telephone lines in the kitchen and master bedroom. Pulsing.

Every night I turn off electricity. This turned on Spruce Knob's battery back up. I removed the back up battery in the fiber optic box inside of my home. Still pulsing.

I terminated my fiber optic account and removed the telephone lines. Still pulsing. I asked Spruce Knob to remove their outdoor box from the exterior wall of my home. They didn't. I did. The box contained an extremely large and heavy back up battery.

https://vimeo.com/724141518?fl=pl&fe=sh

https://airestech.com/blogs/digital-wellness/wellness-tips-for-college-students-on-campus-and-beyond

https://airestech.com/blogs/digital-wellness/lyme?srsltid=AfmBOor3np0YxpC99-hmsEYKyPYLidOHLm38AjRClT-iz5N-y3epzZzN

Hi, I am currently looking into getting some internet. I know the most ideal would be a solution without any Wi-Fi at all, but at this stage it is not feasible for me.

I do however want to reduce as much exposure as possible, and hence will for example disable Wi-Fi when not needed, especially at night.

My question now is which option would be better in terms of health:

1) Fiber + Wi-Fi - Sadly the only fiber socket I have would be in the living room. The closest I would be to it is probably around 3Meters (not ideal), but I suppose in those cases wifi could be turned off, and an Ethernet can be used for the TV instead. But, when Wi-Fi is on, it will be in a quite central area (living room)

2) 5G router. The main benefit would be that I can place this anywhere albeit that devices can still connect to it. However, there is of course a 5G connection to a cell tower which is the main draw back.

Would option 2 be better because I could potentially be further away from the router? Or does the 5G cell tower connection completely negate that benefit, at which point 1 might be the better option even if it is situated potentially closer to me?

Part 1 is at:

[Censorship] Posts and comments in r/electromagnetics are being removed but not by present mods. Bulk of removals are not reported in moderation log.

https://www.reddit.com/r/Electromagnetics/comments/1vhc7r0/censorship_posts_and_comments_in/

In Old Reddit Desktop, on the right hand side of "published and removed posts" is a drop down menu: last 7 days, last 30 days and last 12 months. This is the first time I have seen this drop down menu. Previously, it was hacked.

Last 12 months 2.3k total posts removed

2.2k from the previous year

On the right side of "published and removed comments" is a drop down menu for last 7 days, last 30 days and last 12 months.

In the past 12 months, 802 total comments removed

752 from the previous year

Some of the removed posts and comments and all of the wikis were by former mod u/microwavedindividual after his account was hacked. Only one person offered to approve them. Thank you u/OatmilkCornFed. u/microwavedindividual was the second top mod commencing when this sub was created. We need more people to approve his removed posts, comments and wikis.

https://www.reddit.com/r/Electromagnetics/comments/1smk2o9/wikis_almost_all_of_our_wikis_were_compiled_by

r/electromagnetics needs archivers to archive newer and future posts into wikis. If later they are removed, people can search for them in the wiki index and mods can restore them by clicking on "approve." Please volunteer.

In Old Reddit Desktop > Growth traffic stats > Reports & Removals >

Removals 36 items removed? 31 from the previous 30 days

Hoover on the ? after "removals 36 items removed" pops up this window:

Jun 28, 2026 - Jul 27, 2026

Comments removed 29

Posts removed 7

Jul 7, 2026 - Aug 5, 2026

Comments removed 31

Posts removed 10

In Old Reddit Desktop > Growth traffic stats > Reports & Removals > Safety filters

A person using the alias "Reddit" removed submissions. From moderation log in Old Reddit Desktop:

9 days ago reddit removed link "Professional EMF/RF Safety Course – Looking for Fe..." by LawfulnessThin5066 (Banned Domain: Links to a URL not allowed on Reddit)

9 days ago reddit removed link "Professional EMF/RF Safety Course – Looking for Fe..." by LawfulnessThin5066 (Crowd Control: This content has been filtered due to crowd control)

I was concussioned while writing this report.

[Censorship] Part 2: Posts and comments in r/electromagnetics are being removed but not by present mods. Last 12 months 2.3k total posts removed 2.2k from the previous year In the past 12 months, 802 total comments removed 752 from the previous year

https://www.reddit.com/r/Electromagnetics/comments/1vizdou/censorship_part_2_posts_and_comments_in/

The following instructions may apply to other fiber optic models as well.

To turn off the Wi-Fi on your Verizon Sagemcom modem, you need to access its web interface through a connected computer or phone. [1, 2, 3]

Step 1: Log In to the Router

Connect: Plug a computer directly into the router using an Ethernet cable (since you will be turning Wi-Fi off).

Open Browser: Open a web browser and type 192.168.254.254 into the address bar, then press Enter.

Credentials:

Enter the Admin Username and Admin Password printed on the sticker attached to the bottom or back of your Sagemcom device. [1, 2, 3, 4, 5]

Step 2: Disable the Wi-Fi Radios

Navigate: Click on the Wireless or Wi-Fi menu tab at the top or side of the screen.

Select Radio: Look for the Radio On/Off or Wireless Enable/Disable setting.

Turn Off: Select Disable or Off for both the 2.4 GHz and 5 GHz bands.

Save: Click Apply or Save Changes at the bottom of the page. [1, 2, 3, 4, 5]

Note: Once you click save, all wireless devices will instantly disconnect, and you will only be able to manage the router via a wired Ethernet cable.

Total of 23 wi-fi signals and five hidden wireless networks inside of the Green Bank post office in zone 3 of the radio quiet zone. On July 28, 2026.

This year, the post office got Starlink internet. Dishy is on the roof. Previously, the post office did not have internet but had a landline phone.

The post office is in a small building. The post office does not use that huge number of wi-fi signals and hidden wireless networks. Why are there? Does Starlink's internet else where broadcast numerous strong signals? Starlink's -40's dBm has extreme strong power. Stronger than any other wifi including HughesNet and stronger than cell towers.

ElectroSmart app.

https://www.reddit.com/r/Electromagnetics/comments/1hbbbdy/meter_apps_bluetooth_is_there_still_a_safe_site/

https://www.elexana.com/metallic-objects-and-electromagnetism

Hi everyone,

I've recently created a practical course on EMF/RF Safety Assessment, based on my experience in RF spectrum management and EMF compliance.

The course covers:

• RF & EMF fundamentals
• ICNIRP exposure guidelines
• Practical EMF measurements
• 4G & 5G exposure assessment
• Real-world case studies
• Safety compliance and reporting

I'm looking for feedback from RF engineers, telecom professionals, and anyone working in EMF compliance. If you have suggestions for additional topics, I'd love to hear them.

If you're interested, here's the course:
https://www.udemy.com/course/professional-emf-rf-safety-assessment-theory-to-practice-d/?couponCode=7E1C53CD8A6B94E5198E

#RFEngineering #Telecommunications #EMF #RFSafety #5G #ICNIRP #SpectrumManagement #WirelessEngineering #ElectricalEngineering

How is signal attenuation measured?

Signal attenuation is measured as the loss of signal power between two points, expressed in decibels (dB) by comparing input vs. output levels.

For example, if a signal drops from +50 dBm (100 W) to +47 dBm, that is 3 dB attenuation (~50% power loss); a drop to +40 dBm is 10 dB attenuation (~90% loss).

Instruments like VNAs or spectrum analyzers measure this across frequency (e.g., –1 dB at 1 GHz vs. –3 dB at 3 GHz), while high-power attenuators are used to safely handle and measure these losses in systems carrying 1 W to several kW, ensuring accurate readings without damaging test equipment.

Is higher or lower attenuation better?

Lower attenuation is usually better if your goal is to deliver as much power as possible.

Lower attenuation means less signal loss. For example, 1 dB (~20% loss) is much better than 3 dB (~50%) or 10 dB (~90%). However, higher attenuation is often used intentionally in RF systems, such as adding 20–30 dB attenuation to safely reduce a +50 dBm (100 W) signal down to a level a spectrum analyzer can handle (-10 dBm to 0 dBm).

https://birdrf.com/rf-equipment/attenuators