Comparing Tohsu mechanical coaxial relay switches for use at 1420 MHz
Good choice — here’s a detailed comparison between the three models you’re considering: Tohtsu CX‑520D, Tohtsu CX‑600N, and Tohtsu CX‑600NL — with a focus on performance at ~1420 MHz (your hydrogen-line band), isolation, insertion loss, mechanical/mounting differences, and suitability for your radio astronomy / receive-switching application.
✅ Summary table of key specs
Here’s a distilled table of the major relevant specs for each model:
| Model | Impedance | Coil / Current | Isolation @ ~1000 MHz | Insertion Loss @ ~1000 MHz | Max Stated Frequency / Power | Mechanical / Mounting Notes |
|---|---|---|---|---|---|---|
| CX-520D | 50 Ω (funkelektronik.eu) | 12 V nominal, ~160 mA at 12 V (wimo.com) | ~46 dB min at 1000 MHz (funkelektronik.eu) | ~0.20 dB max at 1000 MHz (funkelektronik.eu) | Up to ~2000 MHz listed; power drops at high freq (150 W at 2000 MHz) (funkelektronik.eu) | Mounting: Four screws in one spec; 3× N-female connectors. Weight ~230 g. (wimo.com) |
| CX-600N | 50 Ω (rfparts.com) | 12 V nominal, ~160 mA at 12 V (wimo.com) | ~28 dB min at 1000 MHz (vhelectronics.sk) | ~0.2 dB at 1000 MHz (vhelectronics.sk) | Spec sheet: frequency up to ~1500 MHz (some up to 2000 MHz) (vhelectronics.sk) | Mounting: Two screws (in one listing) ; 3× N-female connectors; weight ~230 g. (The DX Shop Limited) |
| CX-600NL | 50 Ω (rfparts.com) | 12 V nominal, ~160 mA at 12 V (rfparts.com) | ~28 dB min at 1000 MHz in some listing (The DX Shop Limited) | ~0.15 dB at 1000 MHz listed in one spec. (wimo.com) | Max frequency ~1000 MHz in some specs (wimo.com) | Mechanical: “angular sockets” version (connector orientation different) (wimo.com) |
🔍 Interpretation with your application in mind (1420.405 MHz interferometry / receive switching)
Since you are working around 1420 MHz (the hydrogen line) with very sensitive receive/interferometry equipment, the following aspects are especially important: insertion loss, isolation, and performance margin at that frequency (since many specs list data up to 1000 MHz and sometimes less). Also, mechanical/connector layout for your installation matters.
CX-520D
- This model has the best stated isolation at 1000 MHz (~46 dB) among the three. The insertion loss at 1000 MHz is ~0.20 dB.
- It is explicitly rated up to ~2000 MHz in its datasheet (e.g., at 2000 MHz it lists ~39 dB isolation and ~0.25 dB loss) (funkelektronik.eu).
- That gives it good margin for your 1420 MHz use case.
- The other specs (coil voltage, connection types) are similar to the others.
- If you are doing high-sensitivity receive, and switching between antenna/feedlines, the higher isolation is beneficial (reduces leakage/crosstalk).
- The only potential drawback: depending on your mechanical space and mounting, it might be larger or differently mounted (four screws in one spec) but weight and size similar.
CX-600N
- The CX-600N has decent spec, but at ~1000 MHz the isolation drops to ~28 dB as listed in one sheet. (vhelectronics.sk)
- While the spec sheet claims up to ~1500 MHz (some say up to 2000 MHz) for the model. (vhelectronics.sk)
- But the stated isolation at high frequency is significantly lower than the CX-520D’s at 1000 MHz (~28 dB vs ~46 dB). That means more potential leakage or less signal isolation at your band.
- For receive switching that might be an issue (depending on what you’re switching, how strong interfering signals are).
- On insertion loss and other specs it is comparable (~0.2 dB at 1000 MHz) which is acceptable.
- The mechanical mounting is straightforward (two screws) and connectors standard.
CX-600NL
- The “NL” variant appears to have mechanical differences (e.g., angular sockets) rather than major electrical improvements. The data indicates similar insertion loss (~0.15-0.2 dB at 1000 MHz) but isolation is again around ~28 dB at 1000 MHz in one listing. (The DX Shop Limited)
- Another important point: some listings state Max frequency 1000 MHz for this model. (wimo.com)
- That means using it at 1420 MHz would be outside the explicitly stated spec margin — i.e., manufacturer did not necessarily guarantee performance beyond 1000 MHz for this variant.
- Given your band is 1420 MHz, that is a strike against it (you’d be using the relay beyond its stated spec envelope).
- The mechanical variation may or may not matter for you, perhaps only if you need the angled connectors or specific panel mounting.
🎯 My verdict & recommendation for you
Given your specific use (dual‐station SDR interferometry at 1420.405 MHz, sensitive receive chains, likely moderate to low TX power but high need for low insertion loss and good isolation), here is how I would prioritise:
- Top pick: CX-520D — it offers the best isolation and is explicitly rated up to ~2000 MHz, giving you good margin at your 1420 MHz band. That extra margin in isolation helps avoid leakage or feed-through into sensitive receivers.
- Second pick: CX-600N — Acceptable, especially if budget or availability pushes you to it, but you accept lower isolation at 1000+ MHz and somewhat less margin. It might be OK for a receive path where you are switching between feeds and TX power is low, but still note the lower isolation.
- Least favourable: CX-600NL — Only consider if you absolutely require the mechanical/connector orientation it provides (angled sockets etc), and you are either only receiving (so lower power) and accept operating outside the stated spec for frequency (1420 MHz > 1000 MHz spec). But for maximum performance margin I’d avoid it for your hydrogen-line work.
If you’re choosing between the Tohtsu CX‐600N and the Tohtsu CX‐600NL coaxial relays, here’s a breakdown of their specs, similarities, differences, and my recommendation — which should help you decide which fits your radio-astronomy or station switching use case.
✅ What they share
Both units are from Tohtsu (Japan) and have very similar core electrical performance:
- SPDT coaxial relay, 50 Ω impedance. (The DX Shop Limited)
- 12 V nominal coil version (for the standard variant) with pull-in voltage around ~9-16.5 V. (rfparts.com)
- Coil current approximately 160 mA at 12 V. (The DX Shop Limited)
- Life expectancy ~1,000,000 operations. (The DX Shop Limited)
- 3× Type-N female connectors (i.e., 3 N-type sockets: common + two throws) in the “N” family. (The DX Shop Limited)
So electrically they are very much alike — good insertion loss, good isolation, etc.
🔍 Key differences
Here are where the subtle (but possibly important) differences lie:
| Parameter | CX-600N | CX-600NL |
|---|---|---|
| Max frequency / power handling data | The CX-600N is listed up to ~2000 MHz (for some specs) and power ratings: e.g., at 50 MHz: 1000 W, at 1500 MHz ~350 W. (vhelectronics.sk) | The CX-600NL spec sheet gives up to ~1000 MHz (some listings) and somewhat lower or less clearly listed power ratings. (wimo.com) |
| Mechanical / connectors / mounting | CX-600N: “Mounting: Two screws” (per spec from one vendor) and standard straight N‐type female connectors. Operational temp –55 to +70 °C in one listing. (Henry Radio) | CX-600NL: “Mounting: Screw mount (4 screws)” in one spec; some listings indicate “angular sockets” (i.e., the N‐type connectors may be angled) versus straight. (wimo.com) |
| Weight | CX-600N: approx 230 g. (The DX Shop Limited) | CX-600NL: listed 240 g in one spec. (wimo.com) |
So the “NL” appears to be a mechanical variant (connector orientation, mounting holes) rather than a major electrical upgrade. One spec source for NL even explicitly states: “In contrast to the CX-600N model, this model has angular sockets.” (wimo.com)
🎯 Which one for your application (e.g., radio-astronomy station, 1420.405 MHz interferometry etc)
Given your use-case (you’re working at ~1420 MHz for hydrogen line work, dual-station/SDR/antenna switching etc), here are my thoughts:
- At 1420 MHz you are in the upper half of the spec range. For the CX-600N the spec sheet shows up to 1500 MHz (e.g., 26 dB isolation at 1500 MHz) and up to 2000 MHz in some listings. (vhelectronics.sk) The CX-600NL spec (in one sheet) shows up to 1000 MHz (though other listings show more). Using it at 1420 MHz would mean you are relying on performance beyond explicitly listed spec in some sources.
- If your switching involves decent RF power (if you’re transmitting, or if switching antenna feedlines with some losses and isolation needs) then the better “stated to 1500-2000 MHz / higher power” spec of the CX-600N gives more margin.
- If your mechanical layout (e.g., rack mounting, connector orientation, space constraints) demands angled connectors or 4-screw mounting, then the CX-600NL might suit better.
- If cost is a factor and you only operate receive or low-power, and you’re comfortable with the spec margins, the NL could suffice.
🔧 My recommendation
Given all that, I would lean towards recommending the CX-600N for your use (astronomy/1420 MHz) unless you have a strong mechanical reason to prefer the NL version. The extra margin in RF frequency/power spec gives a bit more headroom, which is wise in an interferometry / sensitive receive chain environment.
If you already have space/connector orientation constraints, go for the CX-600NL, but check carefully the exact spec sheet from the vendor (some lists may cap at 1000 MHz or list lower power at that frequency) and ensure it meets your transmit/receive isolation/power needs.
If you like, I can pull together full datasheet comparisons side-by-side (PDF extracts) for both models so you can inspect the full spec tables (isolation vs frequency, insertion loss vs frequency, power vs frequency, physical dimensions) — would that be useful to you?
Great — here are side-by-side key datasheet excerpts and links for the two relays Tohtsu CX‑600N and Tohtsu CX‑600NL, especially focused for your radio-astronomy application at ~1420 MHz. I’ve highlighted the specs relevant for your interferometry / antenna switching use. If you like I can send full PDF links.
CX-600N (Tohtsu)
Key specs:
- Impedance: 50 Ω. (rfparts.com)
- Coil: 12 V nominal (many listings) with pull-in around 9-17 V. Current ~160 mA at 12 V. (The DX Shop Limited)
- Switching speed: Pull-in ≦ 20 ms, drop-out ≦ 15 ms. (docs.rs-online.com)
- Mechanical: SPDT (single-pole double-throw), 3 × N-type female connectors. Weight approx 230 g. Mounting: two screws. Operational temp -25 °C to +50 °C (some vendor says -55 to +70). (The DX Shop Limited)
- RF/High-frequency performance:FrequencyVSWR MaxIsolation (min)Insertion Loss (max)Max RF Power (approx)50 MHz1.0360 dB0.07 dB~1 kW PEP (1.0 CW) (The DX Shop Limited)150 MHz1.1048 dB0.10 dB~1 kW PEP (The DX Shop Limited)500 MHz1.1537 dB0.15 dB~800 W CW (The DX Shop Limited)1000 MHz1.2028 dB0.20 dB~500 W CW (vhelectronics.sk)1500 MHz1.2026 dB0.20 dB~350 W CW (vhelectronics.sk)2000 MHz1.2523 dB0.23 dB~100 W CW (vhelectronics.sk)
- Notes: One spec says “for use up to 1.5 GHz, for 1 kW PEP.” (vhelectronics.sk)
Take-away for your use: At 1420.405 MHz (your hydrogen-line work) this model still has a stated spec up to 1500 MHz with about 26 dB isolation and ~0.2 dB insertion loss. That gives you fairly strong performance margin especially for receive switching or moderate power use.
CX-600NL (Tohtsu)
Key specs:
- Impedance: 50 Ω. (mecheltron.info)
- Coil: 12 V nominal (voltage range ~10-14 V). Current ~160 mA at 12 V; coil resistance about 75 Ω. (wimo.com)
- Switching speed: Pull-in ≤ 20 ms, drop-out ≤ 15 ms. Life expectancy ~1,000,000 ops. (mecheltron.info)
- Mechanical: SPDT, 3 × N-type female connectors. Weight approx 240 g. Mounting: either four screws or two. Operational temp -25 °C to +50 °C. One vendor says “in contrast to CX-600N model, this model has angular sockets.” (wimo.com)
- RF performance (one sheet):FrequencyVSWR MaxIsolation (min)Insertion Loss (max)Max RF Power (approx)50 MHz1.0360 dB0.07 dB~1000 W PEP (mecheltron.info)150 MHz1.1048 dB0.09 dB~1000 W (mecheltron.info)500 MHz1.1535 dB0.10 dB~800 W (mecheltron.info)1000 MHz1.2028 dB0.15 dB~500 W (mecheltron.info)
- One vendor spec sheet mentions “Max. Frequency [MHz] 1000 MHz” for this model. (wimo.com)
Take-away for your use: The NL version appears to have slightly lower stated maximum frequency (1000 MHz in one spec) and slightly lower isolation figures at higher frequencies (e.g., 500 MHz isolation 35 dB vs the 37 dB in the N version for 500 MHz) which might indicate it is more optimised mechanically (e.g., connector types/orientation) rather than for ultra-wide HF/UHF frequency margin. For use at ~1420 MHz you’d likely be beyond the explicitly stated max in some listings (1000 MHz), so you’d be relying on the device working outside stated spec.
Side-by-Side Summary for Your Application
| Spec | CX-600N | CX-600NL | Comments for your ~1420 MHz use |
|---|---|---|---|
| Stated max frequency | Up to ~1500 MHz (some say 2000 MHz) (vhelectronics.sk) | Up to ~1000 MHz (in some spec) (wimo.com) | At 1420 MHz CX-600N gives more head-room. |
| Isolation at ~1000 MHz | ~28 dB for 1000 MHz. (The DX Shop Limited) | ~28 dB for 1000 MHz also listed in one spec for NL. (mecheltron.info) | Comparable at 1000 MHz, but CX-600N also gives data beyond that. |
| Insertion loss at ~1000 MHz | ~0.2 dB. (vhelectronics.sk) | ~0.15 dB (in one spec). (mecheltron.info) | Both good. Slight difference negligible. |
| Mechanical differences | Standard straight connectors, two-screw mount. | Possibly angled sockets, four-screw mount. (wimo.com) | Choose based on panel/connector layout. |
| Mounting & size | ~230 g, two screws. (docs.rs-online.com) | ~240 g, four screws or variant. (mecheltron.info) | Similar ball-park. |
| Cost / availability | Typically slightly higher price (based on listings). | Slightly lower in some listings. | For your application the extra spec margin may justify cost. |
My Recommendation (in your context)
Since you are working in radio-astronomy and specifically at 1420.405 MHz (the neutral hydrogen line), I’d lean strongly toward the CX-600N model for the following reasons:
- It has a stated spec up to 1500 MHz (and even data at 2000 MHz) which gives you better confidence at 1420 MHz (which is above 1000 MHz).
- The isolation vs frequency curve shows that at 1500 MHz it still maintains ~26 dB isolation and ~0.2 dB loss. That gives you comfortable margin.
- Unless your mechanical mounting or connector orientation strongly requires the “NL” variant (angular sockets, specific mounting), the extra spec margin is valuable in sensitive receive / interferometry switching environments (where leakage, isolation, insertion loss matter).
If you do have a mechanical constraint (e.g., limited rack depth, angled connector required) and you are only using it in receive mode (low power) and not transmitting high RF power, the CX-600NL could suffice — but you’d be knowingly working closer to the spec edge at ~1420 MHz.