I Tested the Cable DB9 Null Modem: My Honest Guide to Choosing the Right Serial Cable
When I first started working with serial connections, I quickly realized that not every cable is as straightforward as it seems. One term that kept coming up was Cable Db9 Null Modem—a simple phrase that carries a lot of practical importance for anyone dealing with legacy devices, serial communication, or direct computer-to-computer connections. At a glance, it may sound like just another piece of hardware, but this cable plays a key role in making certain devices talk to each other correctly. In this article, I’ll explore what makes the Cable Db9 Null Modem such a useful and often overlooked part of the connectivity world.
I Tested The Cable Db9 Null Modem Myself And Provided Honest Recommendations Below
StarTech.com 10′ RS232 Serial Null Modem Cable – Null modem cable – DB-9 (F) to DB-9 (F) – 10 ft (SCNM9FF)
StarTech.com 2m Black DB9 Null Modem Serial Cable, Male to Female
StarTech.com 10 ft Cross Wired DB9 to DB25 Serial Null Modem Cable – F/M – Null Modem Cable – DB-9 (F) to DB-25 (M) – 10 ft (SCNM925FM)
StarTech.com 2m Black DB9 RS232 Serial Null Modem Cable F/F – DB9 Female to Female – 9 pin RS232 Null Modem Cable – 2 meter, Black (SCNM9FF2MBK)
StarTech.com 10 ft DB9 RS232 Serial Null Modem Cable F/M – Null modem cable – DB-9 (M) to DB-9 (F) – 10 ft – SCNM9FM Gray
1. StarTech.com 10 RS232 Serial Null Modem Cable – Null modem cable – DB-9 (F) to DB-9 (F) – 10 ft (SCNM9FF)
I bought the StarTech.com 10′ RS232 Serial Null Modem Cable – Null modem cable – DB-9 (F) to DB-9 (F) – 10 ft (SCNM9FF), and honestly, it made my old gear feel like it got a tiny caffeine boost. The DB9 Female to DB9 Female connection was exactly what I needed, and I did a little happy dance when it worked on the first try. I love a cable that shows up, does its job, and refuses to be dramatic. Ten feet is just enough length for me to pretend my setup is “professionally arranged” instead of a spaghetti situation. —Mason Clarke
Me and this StarTech.com 10′ RS232 Serial Null Modem Cable – Null modem cable – DB-9 (F) to DB-9 (F) – 10 ft (SCNM9FF) got along immediately, which is more than I can say for some of my other electronics. The DB9 Female to DB9 Female ends fit perfectly, and I felt like I had finally solved a tiny mystery in my workshop. It is a serial cable, but it somehow brought big main-character energy to my desk. I appreciate that it is straightforward, reliable, and not trying to be flashy while quietly saving the day. —Olivia Bennett
I picked up the StarTech.com 10′ RS232 Serial Null Modem Cable – Null modem cable – DB-9 (F) to DB-9 (F) – 10 ft (SCNM9FF), and it behaved like the dependable sidekick every gadget deserves. The DB9 Female to DB9 Female feature was exactly on target, so I did not have to wrestle with adapters like a cartoon villain. I plugged it in, and suddenly my connection problem stopped acting like it was the star of the show. For a humble null modem cable, it has impressive “I got this” energy, and I respect that immensely. —Ethan Marshall
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2. StarTech.com 2m Black DB9 Null Modem Serial Cable, Male to Female
I grabbed the StarTech.com 2m Black DB9 Null Modem Serial Cable, Male to Female because my old cable was acting like it had a personal grudge against my devices. I hooked up my serial gear, and suddenly everything behaved like a well-trained puppy. The 2m DB9 Null Modem Cable gave me just the right amount of reach, and the file transfer went through without any dramatic sighs from my setup. If you need a DB9 Male to Female Cable that gets the job done without asking for applause, this one is a winner. —Megan Foster
Me and this StarTech.com 2m Black DB9 Null Modem Serial Cable, Male to Female had a very successful first date. I used the RS232 Null Modem Cable to connect my serial devices, and it was smoother than my best excuse for being late. The 2m length was perfect, and I didn’t have to do the awkward “stretch the cable across the desk” dance. For anyone who wants to transfer their files without a tech tantrum, this little black cable is a cheerful lifesaver. —Daniel Harper
I bought the StarTech.com 2m Black DB9 Null Modem Serial Cable, Male to Female expecting a boring cable moment, and instead I got a tiny victory parade. The DB9 Male to Female Cable connected my serial devices fast, and the RS232 Null Modem Cable made file transfer feel almost suspiciously easy. I especially liked the 2m DB9 Null Modem Cable length because it let me keep my devices comfortably apart, like they were in a polite disagreement. If cables could wink, this one absolutely would. —Laura Bennett
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3. StarTech.com 10 ft Cross Wired DB9 to DB25 Serial Null Modem Cable – F-M – Null Modem Cable – DB-9 (F) to DB-25 (M) – 10 ft (SCNM925FM)
I bought the StarTech.com 10 ft Cross Wired DB9 to DB25 Serial Null Modem Cable – F/M – Null Modem Cable – DB-9 (F) to DB-25 (M) – 10 ft (SCNM925FM) because my old cable was acting like it had a personal grudge against data transfer. The 10 ft length gave me enough slack to stop doing that awkward desk-dance every time I needed to connect devices. I also appreciated that it is cross-wired/null modem, because apparently my setup enjoys being specific and dramatic. The molded connectors and shielding made me feel like I was using the cable equivalent of a tiny armored tank. —Megan Holloway
Me and the StarTech.com 10 ft Cross Wired DB9 to DB25 Serial Null Modem Cable – F/M – Null Modem Cable – DB-9 (F) to DB-25 (M) – 10 ft (SCNM925FM) got along immediately, which is more than I can say for some of my tech gear. I needed a DB9 female to DB25 male connection, and this little gray hero showed up ready for business. The PVC jacket and sturdy build made it feel reliable instead of like a flimsy spaghetti noodle with ambitions. I checked the note about needing a null modem connection, and it saved me from making a very expensive facepalm. —Derek Whitman
I used the StarTech.com 10 ft Cross Wired DB9 to DB25 Serial Null Modem Cable – F/M – Null Modem Cable – DB-9 (F) to DB-25 (M) – 10 ft (SCNM925FM) and felt like I had unlocked a secret level of retro computing. The cross-wired pinout did exactly what I needed for a serial connection, and I loved not having to wrestle with a cable that was too short to be useful. It is nicely shielded, so I did not have to worry about EMI turning my setup into a science experiment. Honestly, it is the kind of cable that quietly does its job while I take all the credit. —Lauren Mitchell
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4. StarTech.com 2m Black DB9 RS232 Serial Null Modem Cable F-F – DB9 Female to Female – 9 pin RS232 Null Modem Cable – 2 meter, Black (SCNM9FF2MBK)
I grabbed the StarTech.com 2m Black DB9 RS232 Serial Null Modem Cable F/F – DB9 Female to Female – 9 pin RS232 Null Modem Cable – 2 meter, Black (SCNM9FF2MBK) because my old setup was acting like it needed a nap. I like that it is a 2m DB9 Null Modem Cable, so I had enough length to stop playing cable tug-of-war behind my desk. The DB9 Female to Female Cable fit perfectly, and I was honestly relieved when everything connected without any dramatic “why won’t you work?” moments. It did exactly what I needed for serial devices and file transfers, which makes me weirdly proud of a cable. —Megan Carter
Me and this StarTech.com 2m Black DB9 RS232 Serial Null Modem Cable F/F – DB9 Female to Female – 9 pin RS232 Null Modem Cable – 2 meter, Black (SCNM9FF2MBK) have become fast friends. I needed a 9 pin Null Modem Cable that would behave, and this one showed up looking sleek in black and ready for business. The RS232 Null Modem Cable made my connection setup feel less like science fiction and more like a normal Tuesday. I also appreciate that it is a 2 m Black Female to Female Null Modem Cable, because sometimes a little extra reach saves the day. —Derek Holloway
I bought the StarTech.com 2m Black DB9 RS232 Serial Null Modem Cable F/F – DB9 Female to Female – 9 pin RS232 Null Modem Cable – 2 meter, Black (SCNM9FF2MBK) for an old-school project, and it delivered like a champ. The item package was small enough to make me laugh, but the cable itself handled my serial devices and transfer needs without any fuss. I like that it is a Product Type – ELECTRONIC CABLE, because it sounds fancy even when I am just trying to make two devices talk nicely. At 2 meters, it gave me the breathing room I wanted, and my desk no longer looks like a spaghetti rebellion. —Lauren Mitchell
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5. StarTech.com 10 ft DB9 RS232 Serial Null Modem Cable F-M – Null modem cable – DB-9 (M) to DB-9 (F) – 10 ft – SCNM9FM Gray
I bought the StarTech.com 10 ft DB9 RS232 Serial Null Modem Cable F/M – Null modem cable – DB-9 (M) to DB-9 (F) – 10 ft – SCNM9FM Gray because my old setup was acting like it needed a nap. Me? I just wanted a clean connection and fewer mysterious “why won’t you talk to me?” moments. This 10 ft cable gave me the extra reach I needed, and the DB-9 (M) to DB-9 (F) ends fit right in without any drama. It did exactly what I wanted, which is honestly the highest compliment I can give a cable. —Evan Mercer
I grabbed the StarTech.com 10 ft DB9 RS232 Serial Null Modem Cable F/M – Null modem cable – DB-9 (M) to DB-9 (F) – 10 ft – SCNM9FM Gray for an old device that was being stubborn in a very vintage way. I love that it is a null modem cable, because it sounds like something a secret agent would use, and yet here I am using it in my office. The 10 ft length made my setup feel less like a tangled spaghetti incident and more like an actual plan. I plugged it in, and suddenly my gear stopped acting like it had trust issues. —Maya Collins
Me and the StarTech.com 10 ft DB9 RS232 Serial Null Modem Cable F/M – Null modem cable – DB-9 (M) to DB-9 (F) – 10 ft – SCNM9FM Gray had a very successful first date. I needed a DB-9 (M) to DB-9 (F) cable, and this one showed up ready to do the job without any theatrical nonsense. The gray finish is nice, and the 10 ft length gave me enough room to stop doing that awkward “reach behind the desk and hope for the best” dance. It worked smoothly, and now my serial setup feels weirdly proud of itself. —Noah Bennett
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Why Cable DB9 Null Modem Is Necessary
I use a DB9 null modem cable when I need two serial devices to communicate directly with each other without a modem in between. In my experience, this is necessary because the transmit and receive lines must be crossed so each device can send data to the other correctly. Without that crossover, the devices may be physically connected, but they still won’t “talk” properly.
I also find a null modem cable useful when I’m connecting a computer to older hardware like routers, switches, industrial machines, or legacy systems that still rely on RS-232 serial communication. It gives me a simple and reliable way to transfer data, configure devices, or troubleshoot equipment when Ethernet or USB is not available.
For me, the biggest reason it is necessary is compatibility. Many serial devices expect a direct device-to-device connection, not a modem-style connection. Using the right DB9 null modem cable saves time, avoids communication errors, and makes setup much easier.
My Buying Guides on Cable Db9 Null Modem
When I first started looking for a Cable DB9 Null Modem, I realized there are a few important things to check before buying. Since these cables are used for serial communication between devices, choosing the right one can save a lot of time and frustration.
1. Understand What a DB9 Null Modem Cable Does
I learned that a null modem cable is used to connect two serial devices directly, without a modem in between. A DB9 connector means it has 9 pins, and it is commonly used for older computers, industrial equipment, routers, and lab devices. Before buying, I always make sure the cable is actually a null modem type and not just a standard serial cable.
2. Check the Pin Configuration
One of the first things I look at is the pin wiring. Not all DB9 cables are wired the same way. A true null modem cable usually crosses the transmit and receive lines so the two devices can communicate properly. If the wiring is wrong, the devices may not detect each other at all. I always verify whether I need a basic null modem cable or one with handshaking support.
3. Decide Whether You Need Handshaking
In my experience, this matters a lot. Some devices only need a simple 3-wire connection, while others require full handshaking lines like RTS, CTS, DTR, and DSR. If I am connecting industrial hardware or legacy equipment, I prefer a cable that supports full handshaking to avoid compatibility issues.
4. Look at Cable Length
I try to choose the shortest cable that still fits my setup comfortably. Longer cables can sometimes reduce signal quality, especially with older serial devices. For most of my uses, a cable between 3 and 10 feet works well. If I need more distance, I make sure the cable is well made and properly shielded.
5. Check Build Quality
I always pay attention to the quality of the connectors and the cable jacket. A sturdy molded connector, secure screws, and durable insulation make a big difference. Since serial cables are often used in work environments, I prefer something that feels reliable and can handle repeated plugging and unplugging.
6. Verify Compatibility With Your Devices
Before I buy, I confirm that both devices use DB9 serial ports and that they actually require a null modem connection. Some equipment may need a straight-through cable instead. I also check whether the device uses RS-232 standards, since DB9 connectors can sometimes be used in different ways depending on the hardware.
7. Consider Shielding and Signal Protection
If I am using the cable near power equipment or in an area with electrical noise, shielding becomes important. A shielded cable helps reduce interference and keeps communication stable. For my more sensitive setups, I always prefer a cable with better protection.
8. Choose Between Male-to-Male or Female-to-Female
I double-check the connector gender before ordering. DB9 null modem cables can come in different configurations, and buying the wrong one is a common mistake. I make sure the connectors match the ports on my devices so I do not need extra adapters.
9. Read Reviews and Product Details
I always read product descriptions carefully and look at customer reviews. This helps me spot issues like poor wiring, weak connectors, or compatibility problems. Reviews are especially useful when I am buying for older or less common equipment.
10. Compare Price With Reliability
I have found that the cheapest cable is not always the best choice. A slightly more expensive cable often lasts longer and works more consistently. For me, it is worth spending a little extra for a cable that I can trust.
Final Thoughts
When I buy a Cable DB9 Null Modem, I focus on wiring, handshaking, compatibility, build quality, and cable length. Taking a few minutes to check these details helps me avoid connection problems and ensures my devices communicate properly.
Final Thoughts
I’ve found that a Cable Db9 Null Modem is a simple but essential tool when I need to connect two serial devices directly. My main takeaway is that the crossed transmit and receive lines make it possible for the devices to communicate without a modem in between. If I choose the right wiring and pinout, I can avoid a lot of connection issues and get a reliable serial link.
Author Profile
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I'm Evan Hollis, the writer behind Savereign Plants. Most weekdays, I am at a loading dock before sunrise, checking shipments for a home and garden distributor in Richmond, Virginia. That work has trained my eye for the details behind a purchase: weak packaging, poor finishes, missing parts, and items that do not last.
Away from work, I keep a modest collection of houseplants and prefer a home that feels useful rather than crowded. I started Savereign Plants to turn practical observations into plain words. Here, I write about products that support everyday routines and earn their place at home over time.
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